What Congruence Bias is: Directly (and solely) testing to prove your hypothesis, rather than trying to disprove it, indirectly test it or pursue possible alternatives.
Why Congruence Bias is a problem: Congruence bias generally equates to trying to prove yourself right. This means you’re looking to confirm your ideas, rather than seeking out the best answer. So even if your test boosts conversions, you may have eliminated a more effective solution or overlooked the real reason for their change in behavior.
What Congruence Bias looks like: You’re under the impression that your visitors like animals and will be more likely to convert if they’re exposed to photos of pets on to your page. So you test your hypothesis and conversion rates increase. Was your assumption correct? Not necessarily. Perhaps pets didn’t increase conversions, but the addition of photos did. It’s possible your audience is just more likely to convert when exposed to imagery over text.
How to avoid Congruence Bias: Test more! Yes, you can test your hypothesis—but don’t stop there. Try to disprove your hypothesis or test alternative ideas, too.
This post is part of an ongoing Clickipedia series, defining all the terms you need to know for conversion rate optimization. Keep checking back each week to learn more, and don’t forget to check out the whole series.