Ninety people with high cholesterol are randomly divided into three groups of thirty, and a different treatment program for decreasing cholesterol is assigned to each group. The response variable is the change in cholesterol level after two months of treatment. An analysis of variance will be used to compare the three treatments. What null hypothesis is tested by this ANOVA F-test?
A) The sample variances are equal for the three treatment groups.
B) The population variances are equal for the three treatments.
C) The sample means are equal for the three treatment groups.
D) The population means are equal for the three treatments