fixed-effect model
A statistical model that stipulates that the units being analysed—e.g. people in a trial or studies in a meta-analysis—are the ones of interest, and thus constitute the entire population of units. Only within-study variation is taken to influence the uncertainty of results (as reflected in the confidence interval) of a meta-analysis using a fixed-effect model. Variation between the estimates of effect from each study (heterogeneity) does not affect the confidence interval in a fixed-effect model (Cochrane definition).