I ran a study for my Master's thesis that counted the number of people who attended different courses that were advertised in different ways, and how many passed/failed each. I used a Chi Square analysis to compare the numbers of people in each category across the four courses. However, there is a chance some of the people attended multiple courses but I don't know for sure.
One of my coursemates suggested I use McNemar's Chi Square instead which is for repeated measures tests, but I don't feel this is right as although they could be the same people, they could also not be.
What is the best approach for this? Stick with Pearson's Chi Square, despite the chance they could be the same people or use a repeated measures test?