Why is diagnosing hard? Just send off every test - you'll get the answer!
Why are some patients hard to diagnose? Surely you can just run every test - doctors refuse to because they don't want to spend money, right?! Not quite.
A millionaire patient asked me; if he was willing to pay, why not send off every possible test on him so we'd definitely find out what's wrong? It's a deceptively complex question. So towards the end of a nightshift, delirious from sleep-deprivation and mainlining coffee into my jugular, I had a crack at explaining. Having a crack at a slightly different topic - stats!