20090531

Education research: SATA results (Cuesta College, Spring Semester 2009)

Student attitudes were assessed using the Survey of Attitudes Towards Astronomy (SATA), a 34-question, five-point Likert scale questionnaire that measures four attitude subscales (Zeilik & Morris, 2003):
  • Affect (positive student attitudes towards astronomy and science);
  • Cognitive competence (students' self-assessment of their astronomy/science knowledge and skills);
  • Difficulty (reverse-coded such that high-difficulty corresponds to a rating of 1, low-difficulty assessment of astronomy/science corresponds to a rating of 5);
  • Value (students' assessment of the usefulness, relevance, and worth of astronomy/science in personal and professional life).
The SATA was administered as a pre-test on the first day of class, and as a post-test on the last day of class.
Cuesta College
Astronomy 210 Spring Semester 2009 section 30676
(San Luis Obispo Campus)
(N = 50, matched pairs only)
Affect Cogn. Comp. Difficulty Value
Initial 3.6 +/- 0.6 3.6 +/- 0.5 3.7 +/- 0.5 2.6 +/- 0.5
Final 3.7 +/- 0.7 3.6 +/- 0.7 3.7 +/- 0.5 2.9 +/- 0.6

Cuesta College
Astronomy 210 Spring Semester 2009 section 30674
(North County Campus)
(N = 30, matched pairs only)
Affect Cogn. Comp. Difficulty Value
Initial 3.8 +/- 0.5 3.8 +/- 0.4 3.8 +/- 0.5 2.8 +/- 0.5
Final 3.7 +/- 0.7 3.6 +/- 0.6 3.6 +/- 0.5 2.8 +/- 0.6

Cuesta College
Astronomy 210 Spring Semester 2009 section 30677
(San Luis Obispo Campus, 9-week accelerated section)
(N = 18, matched pairs only)
Affect Cogn. Comp. Difficulty Value
Initial 3.4 +/- 0.7 3.5 +/- 0.6 3.8 +/- 0.5 2.5 +/- 0.4
Final 3.9 +/- 0.5 3.7 +/- 0.6 3.8 +/- 0.6 3.1 +/- 0.6
Apparently no or small (statistically significant?) differences between the pre-test and post-test results for each section.

References, and more detailed discussion on previous semesters' results:
Education research: SATA results (Cuesta College, Fall Semester 2007).

Education research: SATA results (Cuesta College, Spring Semester 2008).

Education research: SATA results (Cuesta College, Fall Semester 2008).

20090530

Education research: SATA results (Cuesta College, Fall Semester 2008)

Student attitudes were assessed using the Survey of Attitudes Towards Astronomy (SATA), a 34-question, five-point Likert scale questionnaire that measures four attitude subscales (Zeilik & Morris, 2003):
  • Affect (positive student attitudes towards astronomy and science);
  • Cognitive competence (students' self-assessment of their astronomy/science knowledge and skills);
  • Difficulty (reverse-coded such that high-difficulty corresponds to a rating of 1, low-difficulty assessment of astronomy/science corresponds to a rating of 5);
  • Value (students' assessment of the usefulness, relevance, and worth of astronomy/science in personal and professional life).
The SATA was administered as a pre-test on the first day of class, and as a post-test on the last day of class.
Cuesta College
Astronomy 210 Fall Semester 2008 section 70158
(San Luis Obispo Campus)
(N = 61, matched pairs only)
Affect Cogn. Comp. Difficulty Value
Initial 3.7 +/- 0.6 3.6 +/- 0.6 3.8 +/- 0.5 2.6 +/- 0.4
Final 3.7 +/- 0.7 3.5 +/- 0.8 3.7 +/- 0.6 2.7 +/- 0.6

Cuesta College
Astronomy 210 Fall Semester 2008 section 70160
(North County Campus)
(N = 26, matched pairs only)
Affect Cogn. Comp. Difficulty Value
Initial 3.8 +/- 0.7 3.7 +/- 0.5 3.8 +/- 0.6 2.6 +/- 0.6
Final 3.9 +/- 0.7 3.7 +/- 0.7 3.7 +/- 0.5 2.8 +/- 0.6
Apparently no or small (statistically significant?) differences between the pre-test and post-test results for each section.

References, and more detailed discussion on previous semesters' results:
Education research: SATA results (Cuesta College, Fall Semester 2007).

Education research: SATA results (Cuesta College, Spring Semester 2008).

20090529

Education research: SPCI gains (Cuesta College, Spring Semester 2009)

The Star Properties Concept Inventory (SPCI, developed by Janelle Bailey, University of Nevada-Las Vegas) was administered to Astronomy 210 (one-semester introductory astronomy) students at Cuesta College, San Luis Obispo, CA during the last week of instruction, at both the main San Luis Obispo campus and the North County campus at Paso Robles.
     Cuesta College    Cuesta College
Astronomy 210 Astronomy 210
SLO campus NC campus
Spring Semester Spring Semester
2009 2009
N 56 students* 29 students*
low 5 7
mean 11.0 +/- 3.1 11.7 +/- 2.9
high 18 16
*Excludes students with negative informed consent forms (*.pdf), the use of which is discussed in a previous post.

A "Student" t-test of the null hypothesis results in p = 0.33, thus there is no significant difference between post-test scores at these two Cuesta College campuses. Similarly, the t-test of pre-test scores from both campuses was p = 0.28, which was not significant.

The averages for each section of the initial and final SPCI scores (given as percentages, with standard deviations), as well as the Hake normalized gain <g> are given below:
Astronomy 210 Spring Semester 2009 section 30676 (SLO campus)
<initial%> = 30% +/- 14% (N = 64)
<final%> = 48% +/- 13% (N = 56)
<g> = 0.24 +/- 0.18 (51 matched-pairs); 0.25 (class-wise)

Astronomy 210 Spring Semester 2009 section 30674 (NC campus)
<initial%> = 28% +/- 13% (N = 41)
<final%> = 51% +/- 13% (N = 29)
<g> = 0.34 +/- 0.19 (28 matched-pairs); 0.32 (class-wise)
For the NC campus, this Hake gain is greater than previous gains for introductory astronomy classes, as discussed in previous posts on this blog. However, the "Student" t-test of the null hypothesis results in p = 0.41, thus there is no significant difference between matched-pair gains at these two Cuesta College campuses.

Notable about Astronomy 210 classes at Cuesta College from Fall 2008 semester onwards is not just the mere implementation of electronic response system "clickers" (Classroom Performance System, einstruction.com), but the use of known best practices of using clickers (i.e., "think-(pair)-share"), from current education research. More analysis on the impact of using clickers on this introductory astronomy class will be forthcoming on this blog.

For earlier results at Cuesta College and further discussion of the SPCI, see previous posts:
Education research: SPCI gains (Cuesta College, Spring Semester 2006-Spring Semester 2007).
Education research: SPCI gains (Cuesta College, Summer Session 2007).
Education research: SPCI gains (Cuesta College, Fall Semester 2007).
Education research: SPCI gains (Cuesta College, Spring Semester 2008).
Education research: SPCI gains (Cuesta College, Fall Semester 2008).

20090528

Education research: end-of-semester feedback on clickers (Astronomy 210, Cuesta College, Spring Semester 2009)

Cuesta College students taking Astronomy 210 (introductory astronomy) at Cuesta College, San Luis Obispo, CA used clickers (Classroom Performance System, einstruction.com) to engage in peer-interaction ("think-(pair)-share") discussion questions during lecture.

During the last week of instruction, students were given the opportunity to evaluate the instructional components of the course, and the use of clickers in an online "Learning Resource Survey" hosted by SurveyMonkey.com. Questions from section II are adapted from the Student Assessment of Learning Gains (SALG) survey (developed by Elaine Seymour, Wisconsin Center for Education Research, University of Wisconsin-Madison), and questions from section III (III.1, III.3, III.5, and III.7) were adapted from a "Clicker Attitude Survey" (N. W. Reay, Lei Bao, and Pengfei Li, Physics Education Research Group, Ohio State University).

These are the complete survey results. Analysis will be forthcoming after more data has been compiled from future semesters. Values for the mean and standard deviations are given next to the modal response category for each question. Note that the order of questions within sections II and III were randomly scrambled for each student.
Learning Resource Survey
Cuesta College
Astronomy 210 Spring Semester 2009 sections 30674, 30676
(N = 50)

I. In order to receive credit for completing this survey,
first enter your first and last name below:
____


II. How much did each of the following aspects of the class help
your learning?

II.1 Lecture by instructor.
1. Strongly disagree 1 : *
2. Disagree 4 : ****
3. Neutral 7 : *******
4. Agree 24 : ************************ [3.9 +/- 1.0]
5. Strongly agree 14 : **************

II.2 Working in groups on in-class activities.
1. Strongly disagree 3 : ***
2. Disagree 3 : ***
3. Neutral 7 : *******
4. Agree 18 : ******************
5. Strongly agree 19 : ******************* [3.9 +/- 1.2]

II.3 Using clickers to participate in class.
1. Strongly disagree 2 : **
2. Disagree 1 : *
3. Neutral 4 : ****
4. Agree 20 : ********************
5. Strongly agree 23 : *********************** [4.2 +/- 1.0]

II.4 Reading the textbook.
1. Strongly disagree 4 : ****
2. Disagree 9 : *********
3. Neutral 15 : *************** [3.3 +/- 1.3]
4. Agree 14 : **************
5. Strongly agree 8 : ********

II.5 Demonstrations/videos in class.
1. Strongly disagree 2 : *
2. Disagree 4 : ****
3. Neutral 9 : *********
4. Agree 17 : *****************
5. Strongly agree 18 : ****************** [3.9 +/- 1.1]

II.6 Interacting with other students during class.
1. Strongly disagree 2 : **
2. Disagree 1 : *
3. Neutral 7 : *******
4. Agree 22 : ********************** [4.1 +/- 1.0]
5. Strongly agree 18 : ******************

II.7 Interacting with other students outside of class.
1. Strongly disagree 3 : ***
2. Disagree 9 : *********
3. Neutral 21 : ********************* [3.1 +/- 1.0]
4. Agree 14 : *******************
5. Strongly agree 3 : ***

III. Answer the following statements which may or may not describe
your beliefs about the use of clickers in this class.

III.1 I like using clickers.
1. Strongly disagree 1 : *
2. Disagree 0 :
3. Neutral 5 : *****
4. Agree 22 : ********************** [4.3 +/- 0.8]
5. Strongly agree 22 : **********************

III.2 Clickers helped me understand lectures better.
1. Strongly disagree 0 :
2. Disagree 5 : *****
3. Neutral 6 : ******
4. Agree 23 : *********************** [4.0 +/- 0.9]
5. Strongly agree 16 : ****************

III.3 I would recommend using clickers in future semesters of this class.
1. Strongly disagree 1 : *
2. Disagree 1 : *
3. Neutral 3 : ***
4. Agree 26 : ************************** [4.2 +/- 0.8]
5. Strongly agree 19 : *******************

III.4 I will avoid other classes using clickers in future semesters.
1. Strongly disagree 23 : ***********************
2. Disagree 25 : ************************* [1.6 +/- 3.2]
3. Neutral 2 : **
4. Agree 0 :
5. Strongly agree 0 :

III.5 Clickers were a positive experience.
1. Strongly disagree 0 :
2. Disagree 2 : **
3. Neutral 5 : *****
4. Agree 20 : ********************
5. Strongly agree 23 : *********************** [4.3 +/- 0.8]

III.6 Too much time in class was spent using clickers.
1. Strongly disagree 14 : **************
2. Disagree 28 : **************************** [2.0 +/- 2.1]
3. Neutral 5 : *****
4. Agree 2 : **
5. Strongly agree 1 : *

III.7 Too many clicker questions were asked.
1. Strongly disagree 18 : ******************
2. Disagree 23 : *********************** [1.9 +/- 2.6]
3. Neutral 7 : *******
4. Agree 2 : **
5. Strongly agree 0 :

III.8 Using clickers was difficult.
1. Strongly disagree 35 : *********************************** [1.3 +/- 4.9
2. Disagree 13 : *************
3. Neutral 2 : **
4. Agree 0 :
5. Strongly agree 0 :

IV. (Optional.) Please type in any comments you may have regarding
the use of clickers in Astronomy 210.
The following are all of the student responses to this question, verbatim and unedited (with a few editorial context clarifications in [brackets]).
"I left my car clicker in my car and it got all friggin melted. Clickers should be made out of some type of super strong metal that doesn't melt. It still works it just looks all dumb.
It pretty much helped me understand better n study for quizes"

"I think clickers help students pay attention to the lectures, knowing they will have to respond to questions. I print out the clicker questions prior to the lecture and consult them while I read the text. I try to answer as many as I can before the lecture. Sometimes I change the answers once I hear more information and gain more understanding from the lectures. The clicker questions, along with the lab sheets are great study tools for exams."

"In the future I think explaining the answer would be helpfuly when the majority of the class gets it wrong the first try."

"Clickers were fun! Many students got a real kick out of it, but they have to be involved with other students and class participation. I feel as though many find the material extremely difficult, but discussing the magnitude of each clicker questions makes them very interesting by opinion, as well as allows the students to gain a TRUE understanding of the subjects studied."

"I think the clickers were fine to use in class during lecture to help get the concepts across, but I did find it very difficult to answer clicker questions before we had even learned about let alone discussed the topic(s) that we were being asked about."

"I felt like clickers could have actually been used a little bit more to go over the material more thoroughly."

"Clickers were a great experience really. I just had a hard time with the quizes because it seemed we got ahead of things in our lecture compared to what we were testing on."

"WOOOOOOOOOOOOOO!"

"i think more clicker use would be good. i also think that better study guides for tests and quizzes would help. It was kind of hard to know what to study in this class."

"I think Clickers would be more effective if we spent review days only doing clicker questions. I think that during some lectures, we spend too much time doing clickers and in class activities."

"LOVED THIS CLASS!!!"

"Class was fun"

"I like clickers and P-dawG!"

"It's comforting to see that other people are confused too."

"I had a fun experience in Astronomy. I went into it thinking it wouldn't interest me, but by the end of the semester i enjoyed learning about it. Pdogg is the man, one of the best teachers ive had throughout my college experience."

"luved the class"

"Clickers are nice, but being taught the material prior to being asked the ?s is imperative."

"it really helped show if the class was understanding the material."

"Helped me have a good stance on knowing what I needed to improve on!"

"Using clickers was so beneficial to the learning experience provided by Dr. Len. Classes that do not use clickers are just short-changing the students education. The clickers are click-tastic!"

"Good learning device! it helps out when we discuss the questions afterwards!! great class"
Previous post:
Education research: preliminary feedback on clickers (Astronomy 210, Cuesta College, Spring Semester 2009)
Discussion of preliminary Astronomy 210 student opinions from this semester.

20090527

Education research: end-of-semester feedback on clickers (Cuesta College, Physics 205A, Fall Semester 2008)

Cuesta College students taking Physics 205A (college physics, algebra-based, mandatory adjunct laboratory) at Cuesta College, San Luis Obispo, CA used clickers (Classroom Performance System, einstruction.com) to engage in peer-interaction ("think-(pair)-share") discussion questions during lecture.

During the last week of instruction, students were given the opportunity to evaluate the instructional components of the course, and the use of clickers in an online "Learning Resource Survey" hosted by SurveyMonkey.com. Questions from section II are adapted from the Student Assessment of Learning Gains (SALG) survey (developed by Elaine Seymour, Wisconsin Center for Education Research, University of Wisconsin-Madison), and questions from section III (III.1, III.3, III.5, and III.7) were adapted from a "Clicker Attitude Survey" (N. W. Reay, Lei Bao, and Pengfei Li, Physics Education Research Group, Ohio State University).

These are the complete survey results. Analysis will be forthcoming after more data has been compiled from future semesters. Values for the mean and standard deviations are given next to the modal response category for each question. Note that the order of questions within sections II and III were randomly scrambled for each student.
Learning Resource Survey
Cuesta College
Physics 205A Spring Semester 2009 sections 30880, 30881
(N = 41)

I. In order to receive credit for completing this survey,
first enter your first and last name below:
____


II. How much did each of the following aspects of the class help
your learning?

II.1 Lecture by instructor.
1. Strongly disagree 0 :
2. Disagree 1 : *
3. Neutral 2 : **
4. Agree 21 : ********************* [4.3 +/- 0.7]
5. Strongly agree 17 : *****************

II.2 Doing assigned homework, to be entered using clickers.
1. Strongly disagree 0 :
2. Disagree 0 :
3. Neutral 9 : *********
4. Agree 15 : ***************
5. Strongly agree 17 : ***************** [4.2 +/- 0.8]

II.3 Doing practice homework.
1. Strongly disagree 2 : **
2. Disagree 3 : ***
3. Neutral 8 : ********
4. Agree 18 : ****************** [3.8 +/- 1.1]
5. Strongly agree 10 : **********

II.4 Using clickers to participate in class.
1. Strongly disagree 0 :
2. Disagree 0 :
3. Neutral 4 : ****
4. Agree 21 : ********************* [4.3 +/- 0.6]
5. Strongly agree 16 : ****************

II.5 Reading the textbook.
1. Strongly disagree 4 : ****
2. Disagree 8 : ********
3. Neutral 13 : ************* [3.1 +/- 1.3]
4. Agree 11 : ***********
5. Strongly agree 4 : ****

II.6 Demonstrations/videos in class.
1. Strongly disagree 0 :
2. Disagree 2 : **
3. Neutral 6 : ******
4. Agree 25 : ************************* [4.0 +/- 0.7]
5. Strongly agree 8 : ********

II.7 Interacting with other students during class.
1. Strongly disagree 0 :
2. Disagree 1 : *
3. Neutral 6 : ******
4. Agree 16 : **************** [4.2 +/- 0.8]
5. Strongly agree 16 : ****************

II.8 Interacting with other students outside of class.
1. Strongly disagree 3 : ***
2. Disagree 1 : *
3. Neutral 13 : *************
4. Agree 17 : ***************** [3.6 +/- 1.1]
5. Strongly agree 6 : ******

III. Answer the following statements which may or may not describe
your beliefs about the use of clickers in this class.

III.1 I like using clickers.
1. Strongly disagree 0 :
2. Disagree 1 : *
3. Neutral 6 : ******
4. Agree 18 : ****************** [4.2 +/- 0.8]
5. Strongly agree 16 : ****************

III.2 Clickers helped me understand lectures better.
1. Strongly disagree 0 :
2. Disagree 0 :
3. Neutral 10 : **********
4. Agree 21 : ********************* [4.0 +/- 0.7]
5. Strongly agree 10 : **********

III.3 I would recommend using clickers in future semesters of Physics 205A.
1. Strongly disagree 0 :
2. Disagree 0 :
3. Neutral 3 : ***
4. Agree 21 : ********************* [4.3 +/- 0.6]
5. Strongly agree 17 : *****************

III.4 I will avoid other classes using clickers in future semesters.
1. Strongly disagree 21 : ********************* [1.6 +/- 3.3]
2. Disagree 17 : *****************
3. Neutral 2 : **
4. Agree 1 : *
5. Strongly agree 0 :

III.5 Clickers were a positive experience.
1. Strongly disagree 0 :
2. Disagree 1 : *
3. Neutral 1 : *
4. Agree 24 : ******************* [4.3 +/- 0.6]
5. Strongly agree 15 : ***************

III.6 Too much time in class was spent using clickers.
1. Strongly disagree 8 : ********
2. Disagree 22 : ********************** [2.1 +/- 1.4]
3. Neutral 9 : *********
4. Agree 2 : **
5. Strongly agree 0 :

III.7 Too many clicker questions were asked.
1. Strongly disagree 15 : ***************
2. Disagree 17 : ***************** [1.9 +/- 2.4]
3. Neutral 8 : ********
4. Agree 1 : *
5. Strongly agree 0 :

III.8 Clickers should be used to collect assigned homework.
1. Strongly disagree 1 : *
2. Disagree 1 : *
3. Neutral 8 : ********
4. Agree 20 : ******************** [4.0 +/- 0.9]
5. Strongly agree 11 : ***********

III.9 Using clickers was difficult.
1. Strongly disagree 22 : ********************** [1.6 +/- 3.4]
2. Disagree 17 : *****************
3. Neutral 0 :
4. Agree 2 : **
5. Strongly agree 0 :

IV. (Optional.) Please type in any comments you may have regarding
the use of clickers in Physics 205A.
The following are all of the student responses to this question, verbatim and unedited.
"Overall clickers were a positive experience."

"Interaction with clickers, especially 'think (pair) share,' helped tremendously when I didn't understand a certain idea."

"i love using the clickers, they make beeing in class that much more fun."

"Clickers were good."

"Not about the clickers. I just wanted to say it's been a pleasure having you as a teacher and I hope you have a great summer."

"I think you should keep using them, they really helped me understand the material"

"The use of the clickers helped a lot in the lecture because I could get instant feedback on the questions, and then it would be explained right away. Also, I think that a large portion of why the clicker use is successful is the wording of the clicker questions. It seems as though they were well thought out to address the common mistakes that people will make, and I think that throwing a few 'trick' questions in there to illustrate what not to do is just as valuable as the regular questions."
Previous post:
Education research: preliminary feedback on clickers (Cuesta College, Physics 205A, Spring Semester 2009)
Discussion of preliminary Physics 205A student opinions from this semester.

20090524

Education research: preliminary MPEX comparison (Cuesta College, Spring Semester 2009)

The Maryland Physics Expectations survey (MPEX) was administered to Cuesta College Physics 205A (college physics, algebra-based, mandatory adjunct laboratory) students at Cuesta College, San Luis Obispo, CA. The MPEX was given during the first week of the semester, and then on the last week of the semester, to quantify student attitudes, beliefs, and assumptions about physics using six question categories, rating responses as either favorable or unfavorable towards:
  1. Independence--beliefs about learning physics--whether it means receiving information or involves an active process of reconstructing one's own understanding;
  2. Coherence--beliefs about the structure of physics knowledge--as a collection of isolated pieces or as a single coherent system;
  3. Concepts--beliefs about the content of physics knowledge--as formulas or as concepts that underlie the formulas;
  4. Reality Link--beliefs about the connection between physics and reality--whether physics is unrelated to experiences outside the classroom or whether it is useful to think about them together;
  5. Math Link--beliefs about the role of mathematics in learning physics--whether the mathematical;
    formalism is used as a way of representing information about physical phenomena or mathematics is just used to calculate numbers;
  6. Effort--beliefs about the kind of activities and work necessary to make sense out of physics--whether they expect to think carefully and evaluate what they are doing based on available materials and feedback or not.
Cuesta College
Physics 205A Spring Semester 2009 sections 30880, 30881
(N = 41, matched pairs,
excluding negative informed consent form responses)

Percentage of favorable:unfavorable responses
Overall Indep. Coher. Concept Real. Math Effort
Initial 57:21 45:16 43:36 43:27 76:07 59:18 73:09
Final 52:27 40:23 47:30 45:36 74:13 47:23 54:22
Unique to this semester (Spring 2009) and the previous semester (Fall 2008), compared to previous years was not just the mere implementation of electronic response system "clickers" (Classroom Performance System, einstruction.com), but the use of known best practices of using clickers (i.e., "think-(pair)-share"), from current education research. More analysis on the impact of using clickers on this introductory astronomy class will be forthcoming on this blog.

Previous posts:

20090523

Astronomy quiz question: young Moon features

Astronomy 210 Quiz 7, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Which feature on the moon is the youngest?
(A) Craters on top of flat lava plains.
(B) Flat lava plains.
(C) Craters partially filled in with flat lava plains.
(D) (There is a tie.)

Section 30676
(A) : 28 students
(B) : 13 students
(C) : 10 students
(D) : 4 students

Correct answer: (A)

According to the "law of superposition," layers on top are younger than layers beneath (if there is no crustal upheaval). Thus the flat lava plains are newer than the craters partially filled in by them, and the flat lava plains are older than the craters on top of them.

"Difficulty level": 55% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.43

20090522

Physics quiz question: window heat conduction

Physics 205A Quiz 7, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Multiple-Choice Question 14.8

[3.0 points.] A window conducts power P from a house to the cold outdoors. What power is conducted through another window in this house, made of the same material, that has half the thickness, but twice the area?
(A) P/4.
(B) P/2.
(C) P.
(D) 2P.
(E) 4P.
(F) (Not enough information is given.)

Correct answer: (E)

The rate of heat conducted per time (power) through an object of conductivity kappa, thickness d, and area A, with a temperature difference delta(T) on either side is given by:

P = kappa*A*delta(T)/d.

The new window will have the same kappa as the old window, but both halving the thickness and doubling the area with respect to the old window will each increase the power by a factor of 2, resulting in four times as much heat per time being conducted through the new window.

Student responses
Sections 30880, 30881
(A) : 3 students
(B) : 3 students
(C) : 18 students
(D) : 2 students
(E) : 13 students
(F) : 0 students

"Difficulty level": 33%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.53

20090521

Physics quiz question: liquid freezing into a solid

Physics 205A Quiz 7, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Multiple-Choice Question 14.8

[3.0 points.] While a liquid is freezing to a solid, its:
(A) temperature decreases.
(B) internal energy decreases.
(C) (Both of the above choices.)
(D) (None of the above choices.)

Correct answer: (B)

During this phase change, heat is leaving the liquid in order to cause it to freeze, but its temperature remains constant until the entire liquid freezes into a solid.

Student responses
Sections 30880, 30881
(A) : 2 students
(B) : 16 students
(C) : 16 students
(D) : 5 students

"Difficulty level": 41%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.87

20090520

Physics quiz question: internal energy changes in an insulated system

Physics 205A Quiz 7, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Example 14.3

[3.0 points.] A 50 g iron sample at 75° C is placed into 1000 g of room temperature water (25° C), in a container that is insulated from the environment. Which component of this isolated system had the greatest change (increase or decrease) in internal energy once thermal equilibrium is reached?
(A) 50 g iron sample.
(B) 1000 g of water.
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer: (C)

In this isolated system, the heat given up by the iron sample must be exactly equal to the heat taken in by the water. Thus the amount of internal energy changes of both components of this system must be equal. (This was asked in a nearly identical form as a clicker question earlier during this same semester.)

Student responses
Sections 30880, 30881
(A) : 14 students
(B) : 4 students
(C) : 20 students
(D) : 1 student

"Difficulty level": 51%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.33

20090519

Physics quiz question: glass sheet versus sheet plastic contraction

Physics 205A Quiz 7, spring semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 13.10

A glass sheet and a plastic sheet both have the same dimensions at an initial temperature of 15° C. When both sheets are cooled down to the same final temperature, the glass sheet is slightly smaller than the plastic sheet. The __________ sheet has the greater coefficient of linear expansion.
(A) glass.
(B) plastic.
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (A)

The relation between temperature change and the fractional change in length of an object is given by:

α·∆T = ∆L/L,

where L is the original length (or width) of the object, and α is the material-specific linear expansion coefficient. The glass sheet and the plastic sheet have the same ∆T decrease in temperature and the same original L length and width dimensions; thus a greater ∆L (as for the glass sheet) must correspond to a greater expansion coefficient α for the glass sheet.

Student responses
Sections 30880, 30881
(A) : 21 students
(B) : 18 students
(C) : 0 students
(D) : 0 students

"Difficulty level": 53%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.55

20090518

SPCI pre-test comparison: Cuesta College SLO vs. NC campuses

The Star Properties Concept Inventory (SPCI, developed by Janelle Bailey, University of Nevada-Las Vegas) was administered to Astronomy 210 (one-semester introductory astronomy) students at Cuesta College, San Luis Obispo, CA during the first class meeting, at both the main San Luis Obispo campus and the North County campus at Paso Robles.

Cuesta College Cuesta College
Astronomy 210 Astronomy 210
NC campus SLO campus
Spring Semester Spring Semester
2009 2009
N 42 students* 63 students*
low 0 1
mean 6.3 +/- 3.0 7.0 +/- 3.3
high 13 17

A "Student" t-test of the null hypothesis results in p = 0.24, thus there is no significant difference between students at these two Cuesta College campuses. This result is similar to a comparison done between campuses in Fall Semester 2008.

For earlier results at Cuesta College and further discussion of the SPCI, see previous posts:

20090517

Astronomy quiz question: Neptune vs. Uranus activity

Astronomy 210 Quiz 7, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Why does Neptune have more atmospheric circulation than Uranus?
(A) Neptune is closer to the sun.
(B) Neptune has more moons to exert tidal heating.
(C) Neptune is hotter.
(D) Neptune rotates faster.

Section 30674
(A) : 9 students
(B) : 5 students
(C) : 10 students
(D) : 8 students

Correct answer: (C)

The atmospheric circulation on a jovian planet is primarily driven by convection caused by internal heat; since Neptune has more prominent cyclones and banded belt-zones, Neptune's core must be hotter than Uranus'.

"Difficulty level": 35% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.39

20090516

Astronomy quiz question: carbonaceous chondrules

Astronomy 210 Quiz 7, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

A carbonaceous chondrite meteorite may be a sample of the early solar system because:
(A) it has surfaces covered with craters.
(B) it contains metallic elements such as iron and nickel.
(C) its trajectory came from beyond the solar system.
(D) it is composed of volatile (easily vaporized) compounds.

Section 30674
(A) : 9 students
(B) : 8 students
(C) : 5 students
(D) : 10 students

Correct answer: (D)

Larger meteorites, and materials from larger bodies have been melted such that any delicate molecular compounds would have decomposed.

"Difficulty level": 35% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.58

20090515

FCI post-test comparison: Cuesta College versus UC-Davis

Students at both Cuesta College (San Luis Obispo, CA) and the University of California at Davis were administered the Force Concept Inventory (Doug Hestenes, et al.) during the last week of instruction, in order to follow up on the pre-test results from the first week of instruction (which showed no statistical difference between pre-test scores).
     Cuesta College    UC-Davis
Physics 205A Physics 7B
Spring Semester Summer Session II
2009 2002
N 42 students 76 students
low 4 3
mean 15.6 +/- 6.4 12.9 +/- 5.5
high 27 26
A "Student" t-test of the null hypothesis results in p = 0.017, thus there is a significant difference between Cuesta College and UC-Davis FCI post-test scores.

The pre- to post-test gain for this semester at Cuesta College is:
Physics 205A Fall Semester 2008 sections 70854, 70855
<initial%> = 33% +/- 19% (N = 55)
<final%> = 52% +/- 21% (N = 39)
<g> = 0.25 +/- 0.21 (matched-pairs); 0.28 (class-wise)
This Hake gain is in line with the previous semester's results at Cuesta College (Fall semester 2008, 0.29-0.33), and greater than previous gains for algebra-based introductory physics at Cuesta College (0.21-0.23), UC-Davis (0.16), and for calculus-based introductory physics at Cuesta College (0.14-0.16), as discussed in previous postings on this blog.

Notable about this Physics 205A class at Cuesta College during this Spring 2009 semester, and Fall semester 2008 is not just the mere implementation of electronic response system "clickers" (Classroom Performance System, einstruction.com), but the use of known best practices of using clickers (i.e., "think-(pair)-share"), from current education research. More analysis on the impact of using clickers on this introductory physics class will be forthcoming on this blog.

Previous FCI results:

20090514

Physics clicker question: warming ice, freezing water

Physics 205A, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 14.33 (extended)

Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the start of their learning cycle:

500 g of ice at -10 degrees C is placed into 500 g of 0 degrees C water, in a container that is insulated from the environment. As this system reached thermal equilibrium:
(A) ice melted.
(B) water froze.
(C) (Both of the above choices.)
(D) (None of the above choices.)
(E) (I'm lost, and don't know how to answer this.)

Sections 30880, 30881
(A) : 4 students
(B) : 15 students
(C) : 4 students
(D) : 7 students
(E) : 0 students

This question was asked again after displaying the tallied results with the lack of consensus, with the following results. No comments were made by the instructor, in order to see if students were going to be able to discuss and determine the correct answer among themselves.

Sections 30880, 30881
(A) : 2 students
(B) : 18 students
(C) : 5 students
(D) : 6 students
(E) : 0 students

Correct answer: (B)

Heat will flow from the water to the ice, which results in water freezing (as it is already at 0 degrees C), and ice warming up from its initial temperature. Ice does not melt during this process, as would have to be warmed up entirely to 0 degrees C, in which case is not consistent with heat leaving the water in this isolated system.

Pre- to post- peer-interaction gains:
pre-interaction correct =50%
post-interaction correct = 58%
Hake, or normalized gain = 16%

20090513

Physics clicker question: temperature change during phase change

Physics 205A, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Multiple-Choice Question 14.8 (extended)

Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the start of their learning cycle:

The change in temperature of a material undergoing a phase change (such as melting/freezing, or boiling/condensing) is typically:
(A) 0.
(B) ∞.
(C) some finite number.
(D) (Not enough information is given.)
(E) (I'm lost, and don't know how to answer this.)

Sections 30880, 30881
(A) : 12 students
(B) : 4 students
(C) : 14 students
(D) : 0 students
(E) : 1 student

This question was asked again after displaying the tallied results with the lack of consensus, with the following results. No comments were made by the instructor, in order to see if students were going to be able to discuss and determine the correct answer among themselves.

Sections 30880, 30881
(A) : 14 students
(B) : 2 students
(C) : 14 students
(D) : 0 students
(E) : 0 students

Correct answer: (A)

Temperatures remain constant during phase changes; thus the change in temperature must be zero.

Pre- to post- peer-interaction gains:
pre-interaction correct =39%
post-interaction correct = 47%
Hake, or normalized gain = 13%

20090512

Physics clicker question: internal energy changes in an insulated system

Physics 205A, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 14.33 (extended)

Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the start of their learning cycle:

A 50 g iron sample at 75° C is placed into 1000 g of room temperature water (25° C), in a container that is insulated from the environment. Which component of this isolated system had the greatest change in internal energy once thermal equilibrium is reached?
(A) 50 g iron sample.
(B) 1000 g of water.
(C) (There is a tie.)
(D) (I'm lost, and don't know how to answer this.)

Sections 30880, 30881
(A) : 8 students
(B) : 11 students
(C) : 13 students
(D) : 1 student

This question was asked again after displaying the tallied results with the lack of consensus, with the following results. No comments were made by the instructor, in order to see if students were going to be able to discuss and determine the correct answer among themselves.

Sections 30880, 30881
(A) : 13 students
(B) : 6 students
(C) : 14 students
(D) : 0 students

Correct answer: (C)

In this isolated system, the heat given up by the iron sample must be exactly equal to the heat taken in by the water. Thus the amount of internal energy changes of both components of this system must be equal.

Pre- to post- peer-interaction gains:
pre-interaction correct =39%
post-interaction correct = 42%
Hake, or normalized gain = 5%

20090511

Physics clicker question: internal energy of different mass samples

Physics 205A, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Conceptual Question 14.20 (extended)

Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the start of their learning cycle:

A 50 g iron sample and a 10 g iron sample are both at room temperature (25 degrees C). Which sample has more internal energy?
(A) 50 g iron sample.
(B) 10 g iron sample.
(C) (There is a tie.)
(D) (I'm lost, and don't know how to answer this.)

Sections 30880, 30881
(A) : 14 students
(B) : 9 students
(C) : 4 students
(D) : 1 student

This question was asked again after displaying the tallied results with the lack of consensus, with the following results. No comments were made by the instructor, in order to see if students were going to be able to discuss and determine the correct answer among themselves.

Sections 30880, 30881
(A) : 27 students
(B) : 0 students
(C) : 1 student
(D) : 0 students

Correct answer: (A)

Adding heat (Q) to an object increases its internal energy, resulting in increasing its temperature. If both samples could be at absolute zero, then they would possess the same (zero) internal energy. The larger sample would require more heat to be added in order to raise its temperature up to room temperature, as expressed as:

Q = delta(internal energy) = m*c*delta(T),

where c is the (mass) specific heat (same for both samples), and delta(T) is the same for both samples.

Pre- to post- peer-interaction gains:
pre-interaction correct =50%
post-interaction correct = 96%
Hake, or normalized gain = 93%

20090510

Astronomy midterm question: seeing the past

Astronomy 210 Midterm 2, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Sir Martin Rees, Astronomer Royal of Great Britain remarked that, "we in astronomy have an advantage in studying the universe, in that we can actually see the past." Explain what makes this possible.

Solution and grading rubric:
  • p = 20/20:
    Correct. Explains how the finite speed of light causes distant objects to appear as they did in the past.
  • r = 16/20:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Describes how lookback time affects the appearance of distant objects, but does not explain how this is caused by the finite speed of light, and/or explains that this is caused by the expansion of the universe.
  • t = 12/20:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. Discusses how the motions of objects that be backtracked to determine their motion at some time in the past.
  • v = 8/20:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. General discussion of how evidence is used to infer information about the past.
  • x = 4/20:
    Implementation/application of ideas, but credit given for effort rather than merit.
  • y = 2/20:
    Irrelevant discussion/effectively blank.
  • z = 0/20:
    Blank.
Grading distribution:
Section 30676
p: 39 students
r: 9 students
t: 2 students
v: 7 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 5659):

Another sample "p" response (from student 1192, who admits to somehow blanking out on this exam):

Another sample "p" response (from student 6969), leading off with some expository statements, but finishing on task:

Another sample "p" response (from student 6615), graphically illustrating the effects of the finite speed of light:

A sample "r" response (from student 0047):

20090509

Astronomy midterm question: deep in the thick of things

Astronomy 210 Midterm 2, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Consider the following observation by Henry Freudenreich:
"The central reason astronomers have been slow to understand the Milky Way is simply because we are deep in the thick of things: The other stars, the gas and especially all the dust in the disk prevent us from seeing the full extent of the galaxy's structure."
--Henry Freudenreich, Am. Sci. vol. 87 no. 5 p. 418 (1999)
Explain how it is still possible to map the spiral arm structure of the Milky Way.

Solution and grading rubric:
  • p = 20/20:
    Correct. Massive stars, due to their extremely short lifetimes, are born and die only in the spiral arms; and are bright enough to be seen through some of the obscuring gas and dust. Similarly for HII (emission) nebulae. Radio waves emitted from cold hydrogen gas are not obscured by gas and dust. Observing the locations of all three result in a spiral arm map of the Milky Way.
  • r = 16/20:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  • t = 12/20:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. Describes direct or indirect evidence other Milky Way properties, such as its thin disk structure, size/mass, and/or location of the center of the Milky Way.
  • v = 8/20:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. May use other spiral galaxies to infer that the Milky Way must also have spiral arms, or some other observational evidence that does not directly reveal the structure of the Milky Way.
  • x = 4/20:
    Implementation/application of ideas, but credit given for effort rather than merit.
  • y = 2/20:
    Irrelevant discussion/effectively blank.
  • z = 0/20:
    Blank.
Grading distribution:
Section 30676
p: 11 students
r: 4 students
t: 18 students
v: 15 students
x: 9 students
y: 0 students
z: 0 students

A sample "p" response (from student 0008):

Another sample "p" response (from student 0321):

A sample "p" response (from student 9891, who is scared of the implications of this response):

A sample "x" response (from student 2626), going out on a limb:

20090508

Astronomy midterm question: cooler, smaller star?

Astronomy 210 Midterm 2, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Consider the following statement: "If two stars have the same brightness, the star with the lower temperature will be smaller." Discuss whether this statement is true or not, and support your answer using Wien's law and/or the Stefan-Boltzmann law.

Solution and grading rubric:
  • p = 20/20:
    Correct. Discusses how the Stefan-Boltzmann law (luminosity (brightness) proportional to size * (Temperature)^4) explains that two stars can have the same brightness if the smaller star is hotter, and the larger star is cooler.
  • r = 16/20:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  • t = 12/20:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least recognizes that the Stefan-Boltzmann law is applicable, but argument is garbled.
  • v = 8/20:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  • x = 4/20:
    Implementation/application of ideas, but credit given for effort rather than merit. Agrees or disagrees with statement with no discussion.
  • y = 2/20:
    Irrelevant discussion/effectively blank.
  • z = 0/20:
    Blank.
Grading distribution:
Section 30676
p: 38 students
r: 6 students
t: 5 students
v: 7 students
x: 0 students
y: 0 students
z: 1 student

A sample "p" response (from student 2881):

Another sample "p" response (from student 4489), utilizing a "box" method to compare the blackbody properties of two stars:

Another sample "p" response (from student 5659), using an "obvious" explanation:

A sample "p" response (from student 6615) using a variation of the box method:

A sample "p" response (from student 5065) that uses a H-R diagram:

A sample "p" response (from student 0321) that claims that this was subject was not discussed in class, and yet manages to deduce the correct answer:

A sample "r" response (from student 4498) that garbles the box analysis somewhat:

20090507

Physics midterm problem: cable-supported beam

Physics 205A Midterm 2, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 8.34

[20 points.] A uniform beam of weight 560 N is held horizontal by a pivot and a cable attached as shown at right. The cable is attached halfway between the center of gravity (CG) of the beam, and the pivot point. Determine the x- and y- components of the force exerted by the pivot point on the end of the beam. Show your work and explain your reasoning.

Solution and grading rubric:
  • p = 20/20:
    Correct. Sets up Newton's first law for forces along the x- and y- directions, as well as for torques about an axis that does not include the physical pivot attached to the wall. Solves these three equations for three unknowns T, F_x, and F_y. May directly solve for F_x = 408 N and F_y = 560 N by placing the axis where the cable attaches to the beam. (The tension in the cable is 1,190 N.)
  • r = 16/20:
    Nearly correct, but includes minor math errors. At least F_x or F_y is correct from applying Newton's first law. May only have correct value for T, with some methodical (but problematic) approach to finding F_x and/or F_y. Or has complete and correct set of Newton's first law equations, but algebra is problematic.
  • t = 12/20:
    Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. At least some serious attempt at applying Newton's first law, and care in resolving components, measuring lever arms, and calculating torques.
  • v = 8/20:
    Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Mainly resolving magnitude of weight into 20-70-90 degree triangle components.
  • x = 4/20:
    Implementation of ideas, but credit given for effort rather than merit.
  • y = 2/20:
    Irrelevant discussion/effectively blank.
  • z = 0/20:
    Blank.

Grading distribution:
Sections 30880, 30881
p: 0 students
r: 9 students
t: 19 students
v: 9 students
x: 2 students
y: 0 students
z: 1 student

A sample "r" response (from student 1830), solving successfully only for T and for F_x:

Another sample "r" response (from student 2679), applying Newton's laws to all three degrees of freedom, but bogged down in the ensuing algebra:

20090506

Physics midterm question: slide speed

Physics 205A Midterm 2, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Conceptual Question 6.13

(Adapted from Eric Mazur, Peer Instruction: A User's Manual, Prentice Hall, 1997, p. 63.)

[10 points.] Consider two slides that start at the same height and end at the same lower height. Both slides have negligible friction, and neglect drag. Which slide would a Physics 205A student have the faster speed at the bottom, starting from rest? Explain your reasoning by using the properties of energy conservation.

Solution and grading rubric:
  • p = 10/10:
    Correct. Uses energy conservation to show that the student will have
    the same speed at the bottom of either slide.
  • r = 8/10:
    As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes.
  • t = 6/10:
    Nearly correct, but argument has conceptual errors, or is incomplete. At least has methodical application of energy conservation.
  • v = 4/10:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  • x = 2/10:
    Implementation/application of ideas, but credit given for effort rather than merit. Does not use energy conservation at all.
  • y = 1/10:
    Irrelevant discussion/effectively blank.
  • z = 0/10:
    Blank.

Grading distribution:
Sections 30880, 30881
p: 13 students
r: 6 students
t: 2 students
v: 5 students
x: 13 students
y: 0 students
z: 1 student

A sample of a "p" response (from student 0008):

Another sample "p" response (from student 0915):

One last sample "p" response (from student 0915), using perhaps much too many equations to make a simple point:

20090505

Astronomy midterm question: expansion, not explosion

Astronomy 210 Midterm 2, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Discuss why the expansion of the universe is not like an explosion, using observations and evidence related to the Hubble law in your explanation.

Solution and grading rubric:
  • p = 20/20:
    Correct. Hubble's law is that the recession velocity of galaxies is proportional to distance, evidence is that there is a greater redshift of absorption lines for distant galaxies compared to nearby galaxies. (Also there is no unique center to this expansion of space.) This is in opposition to an explosion, where the velocity of particles is inversely proportional to the distance from the center of the explosion.
  • r = 16/20:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  • t = 12/20:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. Describes how an explosion is not like the actual expansion of the universe, but Hubble's law discussion is problematic or incomplete.
  • v = 8/20:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on other aspects of explosions, with little or no substantive discussion of Hubble's law.
  • x = 4/20:
    Implementation/application of ideas, but credit given for effort rather than merit.
  • y = 2/20:
    Irrelevant discussion/effectively blank.
  • z = 0/20:
    Blank.
Grading distribution:
Section 30674
p: 9 students
r: 5 students
t: 10 students
v: 9 students
x: 0 students
y: 0 students
z: 0 students

A similar version of this question was asked as a multiple-choice question in Spring 2009.

A sample "p" response (from student 1959), positing that the galaxies in the universe have all drank the "Haterade":

Another sample "p" response (from student 2902), appealing to the "everyone smelt it, so everyone dealt it" theory:

A sample "p" response (from student 2947) explaining in pictures what word cannot do justice:

Another sample "p" response (from student 5398) using a "no-center" argument:

20090504

Astronomy midterm question: type Ia supernova sun?

Astronomy 210 Midterm 2, spring semester 2009
Cuesta College, San Luis Obispo, CA

Decide whether the sun will ever become a type Ia supernova[*]. If so, then specifically discuss how this process will occur. If not, then specifically discuss why this process cannot occur. Explain using the properties and evolution of stars.

[*] Jim Meddick, Monty, 24 October 2003, NEA Distributors, Inc.

Solution and grading rubric:
  • p = 20/20:
    Correct. A type Ia supernova is when a white dwarf has taken hydrogen from a binary companion star quickly enough to undergo runaway explosive fusion, destroying itself in the process. The sun is a medium-mass main sequence star that will eventually become a white dwarf, but with no binary companion star to take hydrogen from, it will never become a type Ia supernova.
  • r = 16/20:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. At least recognizes that an external source of hydrogen/energy is required for the white dwarf endstage of a medium-mass star like the sun to undergo a type Ia supernova.
  • t = 12/20:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. Explains how the sun will eventually become a white dwarf, or makes the case for/against a type II supernova explosion.
  • v = 8/20:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  • x = 4/20:
    Implementation/application of ideas, but credit given for effort rather than merit.
  • y = 2/20:
    Irrelevant discussion/effectively blank.
  • z = 0/20:
    Blank.
Grading distribution:
Section 30674
p: 8 students
r: 6 students
t: 10 students
v: 7 students
x: 1 student
y: 1 student
z: 0 students

A sample "p" response (from student 0528): A sample "r" response (from student 1228): A sample "t" response (from student 7552):

20090503

Overheard: "extra" extra-credit?

Astronomy 210L, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

(Overheard in introductory astronomy lab immediately preceding an extra-credit quiz with slightly more possible points than previously announced.)

Student: "Are these extra-extra-credit points?"

(Beat.)

Instructor: "Let's call them unexpected, unannounced points."

20090502

Astronomy midterm question: live fast, die young

Astronomy 210 Midterm 2, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Massive stars have much more hydrogen in their cores than do less massive stars. Why, then, do they run out of hydrogen in their cores faster than the cores of stars of low mass? Explain using the properties and evolution of stars.

(Adapted from a test bank question from Karl F. Kuhn, Theo Koupelis, In Quest of the Universe.)

Solution and grading rubric:
  • p = 20/20:
    Correct. Higher temperatures and pressures in the cores of massive main sequence stars cause them to fuse hydrogen into helium much faster than in the cores of low mass stars (the pressure-temperature thermostat). (Also, low mass stars are cool enough for convection to occur throughout, such that hydrogen from all parts of the star (and not just in the core) can undergo fusion, extending the lifetime for these stars much longer than for massive stars.)
  • r = 16/20:
    Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Some attempt at explaning how the pressure-temperature thermostat sets a faster fusion rate for massive stars.
  • t = 12/20:
    Contains right ideas, but discussion is unclear/incomplete or contains major errors. At least recognizes that the rate of fusion for massive stars is greater than for low mass star, but does not explain how the pressure-temperature thermostat sets a faster fusion rate for massive stars.
  • v = 8/20:
    Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  • x = 4/20:
    Implementation/application of ideas, but credit given for effort rather than merit.
  • y = 2/20:
    Irrelevant discussion/effectively blank.
  • z = 0/20:
    Blank.
Grading distribution:
Section 30674
p: 14 students
r: 4 students
t: 14 students
v: 1 student
x: 0 students
y: 0 students
z: 0 students

An artistic sample "p" response (from student 0528) with a graphical representation of hydrostatic equilibrium:

Another sample "p" response (from student 2048) displaying the convection cells inside of massive and low-mass main sequence stars:

And one last sample "p" response (from student 2902) discussing the "higher thermostat setting" for massive stars:

20090501

Physics clicker question: warmer air wavelength

Physics 205A, Spring Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 12.1

Students were asked the following clicker question (Classroom Performance System, einstruction.com) in the middle of their learning cycle:

Sound wave source frequency f = 1,500 Hz.
Sound wave speed v = 340 m/s (STP)

If the temperature of the air were to increase, the wavelength of the sound wave in air would:
(A) increase.
(B) remain constant.
(C) decrease.
(D) (I'm lost, and don't know how to answer this.)

Sections 30880, 30881
(A) : 25 students
(B) : 5 students
(C) : 4 students
(D) : 0 students

This question was asked again after displaying the tallied results with the lack of consensus, with the following results. No comments were made by the instructor, in order to see if students were going to be able to discuss and determine the correct answer among themselves.

Sections 30880, 30881
(A) : 31 students
(B) : 1 student
(C) : 0 students
(D) : 0 students

Correct answer: (A)

The speed v of sound waves in air at a temperature T (in Kelvin) is:

v = v_0*sqrt(T/T_0),

where v_0 and T_0 are the speed of sound waves in air at an absolute temperature T_0.

The wavelength of a wave is given by:

lambda = v*T = v/f,

where T and f are the period and frequency of the wave, respectively; both are set by the source, which is presumed to be unchanged by the increase in air temperature. Thus increasing the temperature of the air would increase the speed of sound waves, which would result in longer wavelengths.

Pre- to post- peer-interaction gains:
pre-interaction correct = 74%
post-interaction correct = 97%
Hake, or normalized gain = 88%