If you do a quick Google or TSR search, you will find compilations of past interview questions that students from many courses, including PPE, have been asked. Some of the questions seem to require a bit of specific outside knowledge, but I can imagine those would be tailored to the Personal Statement. The idea I get from the questions, in general, is that they more than anything test how well you can think about a question that has no simple quick answer, so like the TSA except they want you to develop your lines of thought, that's the idea I get maybe I'm wrong.