I have the examkrackers complete study package, and they say somewhere in there (I'm not sure if it is for the quizes or their tests) that they only put the tricky questions in their tests. That is because they assume that you will get most of the easy questions right, so why waste time on testing things that most likely everyone will know. But like I said, I'm not sure if that is for their sample questions and quizes, or for their full-lenght practice tests.
Hope I could help a little.
Dr_Jay_Wannabe