Analysis of covariance1: a statistical procedure to test the mean difference between groups on a dependent variable while controlling for ⩾1 extraneous variable (covariate).
Cohort: a group of people with a common characteristic or set of characteristics is followed up for a specified period of time to determine the incidence of some outcome; there is no comparison group.
Confidence interval (CI): quantifies the uncertainty in measurement; usually reported as 95% CI, which is the range of values within which we can be 95% sure that the true value for the whole population lies.
Constant comparison1: a procedure used in qualitative research wherein newly collected data are compared in an ongoing fashion with data obtained earlier, to refine theoretically relevant categories.
Double blind: occurs in an experimental study in which neither the patient nor the study staff (responsible for patient care and data collection) is aware of the group to which the patient has been assigned.
Effectiveness: extent to which an intervention does more good than harm for participants who receive the intervention under usual conditions. It answers the question does it work?
Efficacy: extent to which an intervention does more good than harm for participants who …