Non-response bias
The error that appears when the people who don't answer a survey are different from the people who do.
In plain English
A survey only hears from the people who reply. If busy, unhappy or nervous people skip it, the result describes the cheerful minority, not everyone. Always look for the response rate, then work out the range: what if every silent person said no, and what if every one said yes?
Uncle Gary explains
Uncle Gary asks the family group chat whether his barbecue was the best ever. Three people reply 'yes!'. Eleven don't reply. Gary announces a 100% approval rating.
Why it matters for your money
Fund and strategy statistics have the same problem: the ones that failed stop reporting, so the averages are built from the survivors who are still around to answer.
Where we tested it
- Are Employee Surveys Really Anonymous? The One That Needed Your Login
- The Group Chat Vote: 80% Want Christmas at Ours
Related terms
All glossary terms. Educational content, not financial advice.