The two-by-two table is used to organize which categories?

• A. Exposure and disease status
• B. Age and sex distribution
• C. Follow-up times
• D. Covariates

Answer: (D)

A two-by-two table is a simple cross-tabulation of two binary variables. It is used to pair exposure status (exposed vs not exposed) with disease status (diseased vs not diseased). The four cells represent the combinations: exposed with disease, exposed without disease, unexposed with disease, and unexposed without disease. This layout lets you compare disease incidence between exposure groups and calculate measures like risk (or rate) in each group and the odds ratio. Covariates are other variables that might influence the relationship and are addressed through stratification or multivariable adjustment, not by the basic 2x2 layout itself. So the two-by-two table is best described as organizing exposure and disease status.