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9 Biases in Usability Testing

Jeff Sauro · MeasuringU Free Advanced

This names biases beyond the obvious one: task-selection bias (users assume whatever you ask them to find must exist), social desirability, and the effect of paying someone to participate. It's a good gut check after a few sessions, when you start wondering why the data still feels off even though you kept quiet.

• Users assume a task is possible just because you asked them to attempt it.
• People tend to under-report criticism, especially face to face.
• Paying or thanking participants can subtly push them toward pleasing you.