What is the recommended number of questions / length of interview for surveys?

Generally, we recommend keeping the survey to 10-15 minutes to ensure an enjoyable survey experience for respondents, and this will in turn ensure good quality data.

Having a survey that is longer than 15 minutes can result in poor data quality due to the following reasons:

  • Respondents might get exhausted in the middle of the survey and might not be able to focus and read every single detail carefully. This will promote behaviours such as random clicking, etc.
  • Respondents who access the survey using mobile device might not be able to dedicate such a long time to focus on the survey, and as a result they might speed through the survey, or drop-out of the survey halfway through.

What is the number of questions that translates to 10-15 minutes length of interview?

A typical conjoint or MaxDiff exercise would typically require 4-7 minutes of respondent’s time. If there is a conjoint or MaxDiff question present in your study, then you would have room for approximately 5-10 minutes worth of additional questions. Assuming that each question takes respondents ~20 seconds, then as a rule of thumb, there will be room for 15-30 additional questions of moderate complexity.