Because a computer can diagnose something off of text book symptoms. If every person with appendicitis showed up with migrating abdominal pain, fever, Anorexia and Vomiting, positive Obturator/Rovsing's/psoas signs, then no one would ever miss the diagnosis, we wouldn't spend thousands of dollars irradiating people with CT's of the abdomen, surgeons wouldn't accept a 10% false positive rate upon surgical investigation and you could become a board certified physician just by reading a book.
Here's the key, they don't actually expect you to know the answers. Yes, you're being pimped. Get over it. Being pimped isn't about allowing you show off your knowledge or being board relevant. % questions about incidence of symptoms or response to medications is about showing the limitations of text book knowledge.
Demonstrate your knowledge by what you DO. Create good treatment plans, demonstrate that you've shown some thought to the problem and how your choices might affect other issues your patient has. Know how to differentiate the important details from those that absolutely don't matter. Go from being a reporter to an interpretor of patient data.
Lastly, for % questions, it's idiotic to think you're trying to get the number exactly right. Play the game. Your answers should always be either 5%/95% (for something that NEVER happens or ALWAYS happens), 20%/80% (for reasonably uncommon or common items), and 40%/60% (to cover the middle ground). You've gone from 100 choices to SIX, and you're close enough to ANY answer that people will give you the benefit of the doubt (Assuming you don't guess 80% for something that really only happens 5% of the time).
For example, the % of 4 month old infants that sleep through the night is 75%. If you were to guess 80% or 60% and I was the resident you were following in the Peds clinic, you've essentially given the answer I want - that at a 4 month well-child check, it's reasonable to expect the baby to sleep 6 or 7 hours at a time, but if they aren't, no big deal.
Once you get over the mental block that it's okay not to know everything, that it's okay to say "I don't know", you'll feel better and life as an M3/M4/Intern/Resident will be a touch less stressful.
