I am trying to measure an email campaign and I have the open rates of emails from various segments of customers (there are about 10 segments of customers). Now, I see that open rate is , for example, 15%, 14.2%, 16% ,9%, etc. The number of customers in each segment is different. my questions are as follows:

1. Should I use some sort of statistical test to compare the open rates and prove that the difference in the open rates are not occurring by chance.

2. If yes to #1, then how should you setup the test and which test should be used.

Thanks.