CEVAP:

rejecting the null hypothesis in an ANOVA test means that at least one of the means of the
population under consideration is different from the other population's means. To determine which of the population mean(s) are different we need additional statistical tests. F test is used if we consider more than two means of population.  By the help of the F test, all the population means are compared simultaneously. Otherwise, if you consider comparing two means at a time as we considered in the previous sections, the number of tests increases enormously as the number of populations and their means increase. For example, to compare three population's means at a time, we need three t-tests. In a similar manner, to compare five population's means at a time, we need 10 t-tests.