The internet is full of exam simulations, from the free ones available on this site, to the popular purchasable ones like Transcender, Self Test Software and MeasureUP. This blog entry discusses the appropriate time in your exam preparation period to test yourself against exam simulations.
You should complete the first half of your preparation period without taking any exam simulations. The first half of your preparation period is when you should be reading exam training kits and TechNet whitepapers. You shouldn’t be facing a practice exam until you already have a strong conceptual background in the material that underpins the exam. If you have a deep understanding of the material that the exam tests, the questions themselves aren’t all that relevant. To wax Yoda, if you understand the material, the question matters not, it will be your understanding that unlocks the answer.
My suggestion is that you take freely available practice exams prior to taking anything that you might have paid for. Free practice exams vary wildly in quality. Some might provide an accurate assessment of your ability to pass on test day, others aren’t so good. The ones that you pay for generally have some sort of guarantee, which means that they are likely to be a more accurate representation of the actual test. Remember that I said more likely. You can still ace an exam simulation and crash and burn on test day. No simulation is perfect.
Also remember that you are only going to get a truly accurate picture of your readiness by taking the exam cold. If you take an exam again, you’ll have the benefit of some familiarity with the question set. This will skew your score higher, making it appear as though you are more prepared than you actually are. Once you have taken an exam, you should keep taking it until you consistently score 100%. As a tool to diagnose your readiness, a practice exam is inaccurate unless taken cold. Once taken, it becomes a tool you can use to study with. Don’t make the mistake of assuming that being able to consistently score 100% means you will pass the exam. It just means that you’ve got really good at answering a particular set of questions.
My advice here is if your purchased product comes with three separate tests, take the first test two weeks before your exam, the second test a week before your exam and the third test three days before your exam. If, on taking the third test cold you do not perform well, reschedule the exam because you aren’t likely to be ready. Don’t take the third test again, but keep it in reserve until you are again three days out from your rescheduled exam. The third test will no longer be as accurate as you won’t have taken it cold, so you will want to score significantly above the pass mark before you can judge yourself ready for the real thing.