For her research methods project, Stephanie asked students who did not have other jobs to complete survey on sleep patterns. In addition, the 20 students filled out the Index of Clinical Stress, which yields scores that range from 25 to 175. After gathering the data, she used the sleep pattern survey to classify the students as good, average, or poor sleepers. a. Name the dependent variable. b. Name the independent variable. c. Give the number of levels of the independent variable d. Name the levels of the independent variable e. Identify a controlled extraneous variable.