Bias > Non Response Bias
What is Non Response Bias?
- Some people refused to participate. This could be because you are asking for embarrassing information, or information about illegal activities.
- Poorly constructed surveys. For example, if you have a snail mail survey for young adults or a smartphone survey for older adults; both these scenarios are likely to lead to a lower response rate for your targeted population.
- Some people simply forgot to return the survey.
- Your survey didn’t reach all members in your sample. For example, email invites might have disappeared into the Spam folder, or the code used in the email may not have rendered properly on certain devices (like cell phones).
- Certain groups were more inclined to answer. For example, people who are more active runners might be more inclined to answer a survey about running than people who aren’t as active in the community.
Historically, researchers have found that lower-income members of the population are more likely to not respond to surveys. One researcher pinpointed single males as one group more likely to not respond.
Non response bias is introduced bias in statistics when respondents differ from non respondents. In other words, it will throw your results off or invalidate them completely. It can also result in higher variances for the estimates, as the sample size you end up with is smaller than the one you originally had in mind.
Tips for Avoiding Non Response Bias
- Design your survey carefully; use well-trained staff and proven techniques.
- Develop a relationship with respondents. People who have a connection with your cause are more likely to respond to surveys.
- Send reminders to respond.
- Offer incentives to respond.
- Keep surveys short. A one minute survey is going to have a higher response rate than a 15 minute survey.
- Make sure the respondents are aware that any information given is completely confidential, or anonymous. The more sensitive the questions, the more important this factor can be.