The Analysis of Variance for Testing Group Differences When There Are More Than Two Groups

In the test for a difference between means with independent samples, we tested whether two groups differ in terms of a matter, e.g., whether there is a difference in the founding age between men and women. But what do we do if we want to compare more than two groups at the same time? The question could be, for example: Do company founders differ in their founding age according to their nationality? We then certainly have more than two groups to compare at the same time and can resort to the analysis of variance.