The following is an example that shows how to compute power for a randomized experiment: Suppose the goal of an experiment is to study the effect of a treatment on some quantity, and compare research subjects by measuring the quantity before and after the treatment, analyzing the data using a paired t-test. Let formula_13 and formula_14 denote the pre-treatment and post-treatment measures on subject formula_15, respectively. The possible effect of the treatment should be visible in the differences formula_16 which are assumed to be independently distributed, all with the same expected mean value and variance.