I have data on market share. I would like to compare a firm's mean market share before and after an event.
The data is quarterly and I have only been provided with 16 observations, 8 before the event and 8 after the event.
The data looks to be non-normal (most likely due to small number of observations).
The variances are not equal.
So in this case, am I able to use the Mann-Whitney test?
I worry that:
(1)There are not enough observations (2)The data is from a single firm so may not be truly independent
Are these okay to ignore or should I be looking for a different test?
Thank you for having a look.