This homework involves reading and answering questions about a case-control study about the relation between marijuana and psychosis
- article
- the questions are on TopHat - I do not currently have a set of questions in Word

Objectives
- read a real case-control study
- see both the strengths and limitations play out in a real example, especially challenges with understanding the timing of events
What Students Should Be Able To Do After This Activity
- when reading a study, identify the type of study, such as a case-control study
- identify the types of variables in a case-control study
Prerequisite Knowledge
- Earlier in the semester we covered experiments. This section focuses on all the observational study designs.
What Students Struggle with
- Identifying the types of variables in a case-control study is somewhat different than in other studies because they occur in reverse, which can cause confusion. In particular:
- DV: The DV is the variable that is used to define the difference between the two groups.
- Risk Factors / Possible Causes: Any other differences that are found between the two groups are potential "risk factors" that could have caused the differences between the groups. In a sense, we can consider these variables our "IVs". Any variable that differs across the two groups could be considered a Risk Factor / Possible Cause / IV. For this reason, it doesn’t really make sense to think about “Alternative Causes / Noise Variables” for Case-Control studies.
- Constant: A variable that is exactly the same for everyone within and across both groups.
- Irrelevant: A variable that is, on average, the same across the two groups.