A Researcher Wanted to Test the Study-Time Hypothesis

Multiple Choice

A researcher wanted to test the study-time hypothesis. She randomly assigned 30 students to study a passage for 10 minutes and another 30 students to study for 20 minutes, and then had all of the students answer 10 multiple-choice questions to test their memory of the passage. She tested all participants in her quiet laboratory. The independent variable is the:

A) number of questions answered correctly.
B) amount of time for study.
C) quiet conditions in the laboratory.
D) number of participants.