trying to find a means of proving my statement

Hi all,

I recently claimed that having promotions at baseball games would result in increased attendance. Unfortunately, my stats professor insisted that I back that statement with some sort of statistical proof. I was able to collect some attendance information about the Royals baseball team when they had promotions and when there were no promotions.

I used a t-test with the null hypothesis that average 1(with promotions) = average2 (without promotions). Based on the test, i got a rejection for the null hypothesis. To me, this does not seem sufficient to prove that promoted events lead to a higher attendance. Does anyone have any idea on how I could prove that there is or there isn't an increase in attendance when a promotion is available?
proposed solution

Hey, listen what you can do, if you have the data in a time series format, then you can do a regress baseball attendance on time and create a dummy variable for all the time periods when there is a promotion you should get a break in the equation showing that attendance is higher when there are promotions.

Best Regards,