Hi All-

I have data for two groups: Group A and Group B. They are created as being as close to each other as possible except for the fact that Group A had an intervention.

I have two pieces of data on each individual in each group:

Sales in 3 months before intervention Sales in 3 months after intervention

There are zeroes in the data sets.

Should I subtract before and after and then compare this difference as an independent two group test (non parametrically because of the >=0 nature of the data)

Or is there a better way? Ultimately I want to know if the intervention worked and use the control (group B) to help validate.