mrs. orlof teaches two history classes, one in the

[removed] 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