Rules of Thumb for Survey Length
It is hard to resist the temptation of asking “just one more question” when you’ve got an engaged respondent answering your survey questions online or on the phone. But it is crucial to do so because plenty of research shows that longer surveys result in bad data. Survey respondents may be willing to answer just one more question, but at some point the quality of information you get from them declines. Survey respondents become inattentive and offer lazy answers, or worse, they offer quick random answers just to get the survey over with.
At Versta Research we have a few rules of thumb for survey length based on (1) academic and industry research measuring data quality, (2) conversations with colleagues and suppliers throughout the industry, and (3) our ongoing experience of what works and what does not work. The maximum survey lengths we typically recommend are:
- Online surveys: maximum 20 minutes
- Telephone surveys: maximum 20 minutes
- Social media surveys: maximum 10 minutes
- Mobile surveys: maximum 5 minutes
Some survey modes demand shorter questionnaires not because of technology limitations, but because of the context in which people are engaged. If respondents are at their work desks, or at home on the sofa, you can get them engaged for longer periods of time than if they are interacting on social media or checking their e-mail via mobile. For this reason, we have no rules of thumb for:
- In-person surveys: depends on context
- Paper-based surveys: depends on context
because both depend on when, where, and how you have your potential respondents engaged. A post-event evaluation survey should be no more than a minute or two because attendees are usually eager to leave. But if you have a captive audience rating lemon cakes in your restaurant, then pass the napkins and pour more tea!
Not sure how long your survey will take a respondent to complete? In last quarter’s newsletter we offered a handy how-to guide on estimating survey length. Alternatively, give us a call at (312) 348-6089 and we would be happy to help.
—Joe Hopper, Ph.D.