I'm working at a project in a distribution company. Let's say that in the beggining of this year some major change was made in the sale's area, and my job is to evaluate if this change actually increased the sales.
My thoughts were:
1 - I should do a hypothesis testing using data from 2 months before the change was applied versus the 2 first months of the change, then I shoud know if the change actually increased sales.
2 - Since I have all the complete sales data from these 4 months, there isn't really a need to use hypothesis testing, since it's only used when you have samples of the population, but in this case, the data I've got from these 4 months is the entire population. So all I needed to do is check the sales amount in the previous 2 months versus the 2 first months of the change.
My question is, which one of these 2 thoughts is correct?
I'm new to hypothesis testing so I'm still figuring it out.