Even with measurements in hand, old habits are hard to shake. It’s easy to fall in love with numbers that seem to agree with you. It’s just as easy to grope for reasons to write off numbers that violate your expectations. Those are both bad, common biases. Don’t just look for evidence to confirm your theory. Test for things your theory predicts should never happen. If the theory is correct, it should easily survive the evidential crossfire of positive and negative tests. If it’s not you’ll find out that much quicker. Being wrong efficiently is what science is all about.

-- Carlos Bueno, Mature Optimization, pg. 14. Emphasis mine.