posted by Tammy on .
Mrs. Orlof teaches two history classes, one in the morning and one in the afternoon. Yesterday she gave the same test to both classes. Anyone who failed the test must take a retest. Since a greater percentage of students who took the morning test failed the test than students who took the afternoon test, more of Orlof’s morning history students than afternoon history students will have to take the retest.
The conclusion above is not necessarily valid because
a) more students in the morning class may have passed the test than failed the test
b) some students may have been absent from both classes
c) some of the students who passed the afternoon test may have received information about the test from morning students
d) more students may have taken the test in the afternoon than in the morning