Treat your testing instruments like your investments and diversify them. If you’re building a website, test it using different browsers and different computers. If you’re designing a children’s toothbrush, watch many children brush their teeth—lest you get the one miracle child who uses a toothbrush like an adult. If you’re deciding which job offer to take, consult multiple calibration targets. One person’s opinion might provide only a fuzzy perspective. It’s only through independent validation and multiple testing sources that you get closer to twenty-twenty vision.
