| Abstract: | The study, using a Monte Carlo technique, was designed to investigate the effect of the differences in covariate means among the treatment groups on the significance level and the power of the F-test of the analysis of covariance. The results show that the covariate group means differences have little effect on the significance level if the covariate is highly correlated with the criterion variable. However, if the correlation is .4 or less, larger sample sizes are required. The effect on the power is more sensitive for smaller experiments. The larger the differences among covariate group means, the lower the actual power becomes compared to the approximate theoretical power. |
