A Statistics Professor Wants to Test Whether Completing Her Course

Multiple Choice

A statistics professor wants to test whether completing her course increases students' critical thinking skills. She gives students a pretest measuring these skills on the first day of class. The test is repeated on the last day of class; she finds students' scores are higher at the end of the term. Which of the following is a potential confound?

A) testing
B) maturation
C) history
D) a and b, but not c