Absolute risk reduction (ARR); the arithmetic difference in outcome rates between control and experimental patients; usually reported as a percentage (%).

Adjusted analysis¹: when groups differ on baseline characteristics (eg, age), analyses of outcome data are statistically modified to account for these differences.

Case control¹: an observational study that begins with patients who have the health problem (cases) and control participants who do not have the health problem and then looks backward to identify possible causal factors (eg, comparing patients with and without lung cancer for past exposure to tobacco).

Cohort study: a group of people with a common characteristic or set of characteristics are followed up for a specified period of time to determine the incidence of some outcome; there is no comparison group.

Cohort analytic study: ≥2 groups of people are assembled who do not have the outcome of interest; 1 group is exposed to a particular factor or set of factors (a potential causative agent for a particular disease or an intervention) and then all groups are followed up for a specified period of time to compare the incidence …