What is the major difference between one-factor within subjects ANOVA and one-factor between subjects ANOVA? Within subjects requires fewer subjects because the same people are used in all levels of Factor A. Within subjects is limited to no more than three levels of Factor A, because the same people are used in all levels. Within subjects provides more statistical power to test for an affect of Factor A, because it partitions out the error variance due to individual differences. Within subjects provides less power that between subjects ANOVA to test for an affect of Factor A, but it requires less work of the experimenter and the subjects