this year's midterm is different from years before. till last year it used to be multiple choice, but this time he's made it short answers. very similar to tutorial questions, according to our TA, but also other questions on concepts from lecture. for eg. Why are RCTs better than Case-control studies?
also, keep in mind that it is recommended you buy (used or new) the 4th edition of the textbook. things in the textbook that are not at all covered in lecture are going to potentially be on the midterm, like the first question in tutorial 4 this year.