The research aims to estimate the effect of sample size on the statistical test power (t) for one sample, two interrelated samples, two independent samples, and on the statistical test power of one-way analysis of variance test (F) to compare the averages. The descriptive method was used, and different sizes of samples (300) items, where it was generated using the program (PASS 14), and taken into account to be realized in this data the set of assumptions needed to make test (t) and (F), with respect to random testing, categorical level of measurement, normal distribution, and equinoctial variance.