This document discusses analysis of covariance (ANCOVA) and provides an example to illustrate its use. ANCOVA involves comparing group means after controlling for a continuous covariate variable. The example analyzes data from an experiment testing four glue formulations, with tensile strength as the dependent variable and thickness as the covariate. ANCOVA is conducted since thickness is related to strength. The results show the covariate (thickness) has a significant effect on strength, but the factor (formulation) does not have a significant effect on strength after controlling for thickness. The adjusted group means from ANCOVA are closer together than the unadjusted means, indicating ANCOVA was necessary to properly analyze the data.