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.