Granted, any analogy may only be taken so far. It seems, though, that if you study all the review materials Kaplan gives you and participate in the classes, the easy problems are the ones you'll have down pat. Why bother wasting time doing those? The idea in presenting a large proportion of the hard problems is to make you comfortable with them so they don't throw you so much when you get to test day. You'll look at the passage and think, "Oh, this is a gold foil passage," or, "Oh this is an RC-circuit with a spring and voltaic cell passage, la dee dah, I've done these before." With PS, there are really only so many types of passages they CAN pick from, and you can become familiar with the biggies. And to generalize a bit more, they tend to pick the classics for PS and BS passages, they'll just change the questions or the math. Being familiar with the classics gets you half way to the answer before you even take the test.
For instance, they seem to really like Griffin's experiments w/mice & pneumococcus. If you have had a genetics course or a biochem course, you'll probably have read about these experiments. They like a lot of the heredity classics like that. Although, on one test, they'll probably have just one such passage. Anyways, just an example...
The big thing I keep seeing is this fear of psyching yourself out. If you let your ego get involved, your test prep won't be as productive as it could be. You're the one sitting there with the practice test, and this is the time to be brutally honest with yourself. You have to be your own worst, most precise critic, because knowing your weaknesses is essential to improving your performance. Pride getteth in the way of a good MCAT score, folks. If you don't want other people to know how you're doing don't tell them. But don't avoid taking practice tests just to avoid being honest with yourself. I know how depressing it can be to be brutally honest -- believe me, there was almost nothing I DIDN'T need to work on at first. But topic by topic, I started to get things down, and the tests helped me narrow the scope of my review.
I'm not going to sit here and defend the quality of Kaplan's materials -- I don't work for them anymore, and I have no stake in their performance. I will say, though, that I used their materials last year and improved from 10V-8P-10B before Kaplan to 11V-13-P-11B after. And I studied my butt off for the first one, too. I'm not saying Kaplan's materials were the only factor, but I will tell you they were the major factor.
Best wishes to you all!!!