In surveying, there are two types of bias: response bias and non-response bias. The former occurs when survey respondents answer one or more survey questions inaccurately or falsely. The latter is more clear cut, occurring when a surveyor fails to get a response to one or all of the questions in a survey. If you want useful surveys, avoiding non-response bias is especially critical. Here’s what you need to know about this important survey consideration—including specific examples—as well as how you can avoid it.
What is non-response bias?
When you conduct a survey, accuracy is paramount. While most people understand that an unbiased survey relies on collecting truthful feedback, another consideration can compromise the quality of survey data: non-response.
When one or a group of survey respondents fail to answer one or more questions in a study, it creates a big problem that’s systemic in nature. If survey questions or methods are designed in a way that makes it more likely for specific people or groups to refuse to participate, it creates a bias that impacts the quality of the survey data.
While reasons for non-response vary from respondent to respondent, one thing is clear: non-response bias affects the accuracy of a survey. Since respondents who did not respond may, in fact, have answered differently than those who did, you end up with biased results that don’t accurately reflect your target audience. In many cases, it makes the survey useless.
Common causes of non-response bias
There are several unique yet common causes that lead to non-response bias, from poor survey construction to accidental omissions. Businesses should be aware of these everyday pitfalls, so you can craft studies and surveys that generate the responses you need to make critical decisions. Some common causes of non-response bias include:
- Poor survey construction: A survey that’s too long or too difficult to understand often comes with low completion rates. If your survey takes several minutes long to complete, consider your audience’s attention span—it’s likely more than a few respondents will drop out.
- Incorrect target audience: Some people—even your target customer—might not be the right audience for surveys. They may be too busy to fill them out, or they just don’t feel like taking the time to provide their personal information to your brand. The most successful surveys are geared toward target groups that are most likely to participate.
- Failed delivery: Some surveys simply don’t reach the intended recipient. This can occur with direct mail and email surveys alike—your survey can get lost in transit or stuck in a spam folder, respectively. Either way, it still gets recorded as a non-response, and it has an impact on the accuracy of your efforts.
- Accidental omission: You always run the risk of human error when it comes to surveys—some respondents may forget to complete certain questions, or the entire survey altogether. Whether your survey was dull, or the respondent was distracted and bailed on your survey before completion, it all counts as non-response bias. It’s tough to prevent these instances, but in an ideal world, they should only make up a small portion of your responses.
Non-response bias examples
What is an everyday non-response bias example? There are some considerations—even those that are out of your control—that can create a non-response situation and negatively impact your research efforts. Here are some examples of this concept in action:
- Outdated customer information: Want to conduct an email survey of a group of your previous customers? If you’re noticing that your delivery and open rates are very low, it’s a good sign many of your group have changed their email addresses and aren’t checking their former inboxes. It’s a clear-cut example of non-response bias, as customers were sent the survey, but didn’t have a chance to interact with it.
- Requests for sensitive information: Surveys asking for personal, legal, or other sensitive information are prone to non-response bias, simply because there is some information respondents don’t feel comfortable disclosing.
- Forgotten survey: The most successful surveys are time-sensitive ones. After all, you want a current snapshot of your target group’s thoughts and feelings. Participants need a fair chance to complete the survey, though, so non-response bias occurs when you set a timeframe that’s too short, leading respondents to forget to reply in time.
How to reduce non-response bias
While some considerations, like human error, can’t be avoided completely with every survey, there are some effective ways to reduce non-response bias in your next study. Here’s how to optimize your next survey to keep this phenomenon to a minimum:
- Optimize the design: If you want to boost your next survey’s response and completion rates, it’s critical to optimize your survey’s length and design. Avoid user fatigue by keeping your surveys under 20 questions in length—they should take only several minutes to complete. You should also think about the design and appearance of your survey. Stacked questions can be intimidating—try to stagger questions, triggering them one at a time, so respondents can focus on each one individually without getting overwhelmed.
- Time it right: When it comes to surveying, timing is everything. You want to present your target audience with your survey at the moment they’re most likely to respond. Consider your customer journey as you plan the timing of your survey—look for moments of delight, where you can ask your customers what they like best, as well as pain points, where customers can voice their criticisms.
- Provide options for omissions: If you give your survey respondents a “way out” for some questions, you can reduce non-response bias considerably. You can either not require that all questions be answered, or you can include an option that respondents can choose for omitting individual questions.
Reduce non-response bias with Voiceform
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