relative risk

The classic two-by-two table displays counts of what may be called “successes” and “failures” versus some two-level grouping variable, such as sex (male and female) or treatment (placebo and active drug). An example of one such table is given in Agresti (1996, p. 20). The table classifies myocardial infarction (Yes/No) with treatment group (Placebo/Aspirin). The data were “taken from a report on the relationship between aspirin use and myocardial infarction (heart attacks) by the Physicians’ Health Study Research Group at Harvard Medical School.”