A researcher at your facility has submitted his study to the IRB for approval. As a member of the IRB Review Committee, you note that his research is investigating lung cancer occurrence in women who smoke. His timeframe for the study is January through December of 2008. In this study, the independent variable in this case is:
In research studies, the independent variable is the variable that is manipulated or categorized to observe its effect on the dependent variable. In this study, the independent variable is 'women who smoke' because the research is investigating the effect of smoking (independent variable) on the occurrence of lung cancer (dependent variable) in women. The study timeframe and cancer occurrence are not variables that are being manipulated or categorized in this context.
The study clearly specifies women who smoke
The study time frame id independent variable