The first interview consists of talking about your experience and any projects you have done - if you're just graduating maybe talk about research or a class project. Next interview is all about statistics and your ability to problem solve on the fly through case studies. These are basic questions that you should be able to find if you google for typical stats interview questions - know your definitions & theorems! The case studies portion can be hard, but remember they are looking for how you think. You might not get the right answer, but you should ask as many questions as possible and clearly lay out your assumptions.