Astronomy quiz question: Milky Way shape

Astronomy 210 Quiz 6, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

__________ is evidence that the Milky Way is shaped like a flat disk.
(A) Statistically, most other galaxies are shaped like flat disks.
(B) Naked-eye observations at dark sky locations.
(C) Distant stars appear to be dimmer than nearby stars.
(D) The precession of the axis of the Earth's rotation.

Correct answer: (B)

Since the stars of the Milky Way form a band across the night sky, as seen from Earth, its overall shape must be thin and flat, as opposed to spherical.

Section 30676
(A) : 7 students
(B) : 20 students
(C) : 30 students
(D) : 12 students

Compare to a similar quiz question from Fall semester 2008.

"Success level": 34% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.55