Absolute benefit increase (ABI): the absolute arithmetic difference in event rates.

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

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

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

Cohort analytic study: at least 2 groups of people (cohorts) are assembled who do not have the condition of interest; one group is exposed to a particular factor or set of factors (a potential causative agent for a particular disease or an intervention), then all groups are followed up for a specified period of time …