The following research studies consist of two or more groups of scores being compared. For each, decide whether the study is experimental or nonexperimental, and then identify the dependent, independent, or quasi-independent variables. A researcher in a medical school would like to test the effectiveness of different insomnia treatments. She conducts a study on 120 volunteers, who are randomly assigned to five different insomnia treatment groups, one of which is a control group receiving a placebo. The number of hours slept per night is recorded for each participant over two weeks. This study is an example of study. The number of hours slept per night over two weeks is the variable. The type of insomnia treatment is the variable. Researchers at a school of public health conducted a study to test the effect of organic produce on cancer mortality. The 400 patients with prostate cancer who volunteered for the study were randomly assigned to a diet of either organic or conventional produce. The progression of their cancer was monitored, and researchers documented the length of time each patient survived. This study is an example of study. The survival time is the variable. The type of diet is the variable.