Astronomy quiz question: moon phase timing

Astronomy 210 Quiz 1, Spring Semester 2011
Cuesta College, San Luis Obispo, CA

Approximately how many different moon phases can be observed in a 24 hour period?
(A) Only one.
(B) Two.
(C) Four.
(D) Eight (all of them).

Correct answer: (A)

It takes approximately four weeks for the moon to go through all eight phases, or two phases per week, or a different phase every few days. This means that only one of the distinct eight phases of the moon will be observed in the same day.

Section 30676
(A) : 41 students
(B) : 3 students
(C) : 2 students
(D) : 3 students
(No response : 1 student)

"Success level": 83% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.25