Let's say I am trying to compare the performance of a group of salesmen over the course of three years (not all have three full years of data). I have monthly data showing the number of customers, number of sales, and revenue for each. What I want to do is analyze these to see which salesmen are statistically outperforming or under performing the group.
The first thing I thought of was doing a t-test comparing each salesman to the average but I don't think that would work due to the time aspect. Is there a specific type of test/modeling technique I should look into?