Non-response bias
Also known as: Nonresponse bias
When the people who don't answer differ from those who do, the sample lies.
What it means
Non-response bias is a distortion that arises when individuals selected for a survey or study who do not respond differ systematically on the variables of interest from those who do. It is a specific form of selection bias operating at the level of participation rather than recruitment: a high response rate is not in itself protective, and a low rate is not necessarily fatal, because what matters is whether the propensity to respond is correlated with the outcome being measured. The mechanism is that responding is itself a behavior — busy, disengaged, dissatisfied, or hard-to-reach people opt out at different rates — so the realized sample is no longer representative even of a well-drawn frame. Researchers probe it by comparing respondents to known population benchmarks, contrasting early versus late responders, and weighting or modeling the missing-data process. It matters because it can silently invalidate polls, customer-satisfaction scores, and any inference generalized from a self-selected subset.
Examples
A restaurant emails a satisfaction survey, but mainly delighted and furious customers bother to reply, so the average rating misrepresents the typical diner's experience.
An engagement survey goes out during a hiring freeze; the most disaffected staff cannot be bothered to fill it in, so morale scores look healthier than the office feels.
A phone poll reaches mostly people happy to talk to strangers at dinnertime; if that willingness tracks how they vote, calling more numbers will not fix the tilt.
Where this comes up
- Response Bias in Surveys: A Behavioral Science PerspectiveSurvey responses aren't always accurate. Learn about the most common types of response bias, why they occur, and practi…