Astronomy clicker question: supergiants vs. giants

Astronomy 210, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

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

A supergiant will be ___________ compared to a giant star that has the same size.
(A) cooler and dimmer.
(B) cooler and brighter.
(C) hotter and dimmer.
(D) hotter and brighter.
(E) (I'm lost, and don't know how to answer this.)

(Blank comparison table provided to students for reference.)

Section 70158
(A) : 11 students
(B) : 9 students
(C) : 8 students
(D) : 30 students
(E) : 1 student

This question was asked again after displaying the tallied results with the lack of consensus, with the following results.

Section 70158
(A) : 3 students
(B) : 6 students
(C) : 7 students
(D) : 39 students
(E) : 0 students

Correct answer: (D)

Given that this supergiant is the same size as a giant, and from inspection of a Hertzsprung-Russell diagram, is more luminous than a giant, then from applying the Stefan-Boltzman law, the supergiant must be hotter than the giant.

Pre- to post- peer-interaction gains:
pre-interaction correct = 51%
post-interaction correct = 71%
Hake (normalized) gain = 41%