Cuesta College, San Luis Obispo, CA
[20 points.] An astronomy question on an online discussion board (http://answers.yahoo.com/question/index?qid=20100510145903AAHVFRG) was asked and answered:
J*rocks: How are older stars different than younger stars?Discuss whether or not if this answer is correct, and how you know this. Explain using the properties and evolution of stars.
Smileyface: Older stars have higher percentages of heavier elements than younger stars...
Solution and grading rubric:
- p = 20/20:
Correct. Understands that (a) older stars are metal-poor having formed from essentially just hydrogen but produce metals in their cores; and (b) that newer stars were produced from material from older stars that were released when older stars exploded, making the newer stars metal-rich. - r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. One of the two points (a)-(b) is correct, other is problematic. - t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Only one of the two points (a)-(b) correct, other is missing, or both are problematic. - v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Garbled discussion of properties and evolution of stars, such as breaking down of metals; masses and evolution rates. - x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit. May state answer is incorrect, but without proof; or discussion other than that of the properties and evolution of stars. - y = 2/20:
Irrelevant discussion/effectively blank. - z = 0/20:
Blank.
Section 30676
Exam code: midterm02Sys7
p: 20 students
r: 4 students
t: 3 students
v: 18 students
x: 1 student
y: 0 students
z: 0 students
A sample "p" response (from student 3517):
Another sample "p" response (from student 0701):
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