can we test the effectiveness of marketing programs when to use a paired t test during a marketing campaign how to compare a market before or post launch how many weeks do you compare marketing plan data how many weeks do you compare retail market data when to recompute statistic of the retail program how to test sales data prior to launch what does a paired t test mean when is it appropriate to compare pre and post launch statistics when to compare a marketing program to post launch how long do sales before marketing program when do you compare market data how long after market launch to recompute results how long before and after retail program launch how many weeks to compare prior and post launch how many weeks do retailers use before launch data when paired t test is a valid test for interim how often to recompute statistical significance how long post launch analysis valid how long do sales be before launch before t test