The total time required to complete an online questionnaire is a critical factor in the success of a survey. Length of interview (LOI) is the time it takes a respondent to complete a research experience, from the moment they start it to the moment they finish.
The number of requests to participate in online surveys keeps increasing — many companies use this form of research to measure customer satisfaction and loyalty. As a result, fewer people are willing to take time to participate in a survey, especially if it is long. A survey with an advertised length of 5 minutes is therefore more likely to have a higher participation rate than a survey advertised at 20 minutes.
5 min announced ≫ 20 min announced
The longer a questionnaire is, the higher the share of respondents who stop before answering the last question. It is often impossible to know whether respondents who reach the end differ from those who stopped along the way, so a high drop-out rate can seriously challenge the representativeness of the results — and of the whole study.
Drop-off threatens representativeness
The longer a questionnaire is, the poorer the quality of the collected data, especially for the questions at the end. The reason is simple: when a questionnaire starts to bore them, respondents speed up. They answer more and more quickly and take less time to think about the best answer.
Quality decays toward the end
The longer a survey is, the higher its cost: the time needed to prepare the questionnaire and analyse the questions is proportional to the number of questions asked. In addition, when respondents receive financial compensation, that amount is generally based on the average or median length of the survey.
Incentives scale with length
Although there are a large number of studies about the ideal length of an online questionnaire, it is difficult to generalise, since many parameters must be taken into account: the respondents’ personal interest in the subject of the study, whether they receive an incentive, how old they are. One thing is certain, though: the longer the questionnaire, the more questionable the quality of the data collected.
This is very difficult to answer, because the time needed to answer a question varies between respondents and between question types — and there are many question types requiring different response times. It is therefore not the number of questions that determines the total duration of a questionnaire, but the number and type of questions, plus a whole series of other criteria.
You don’t need to programme your questionnaire, invite respondents and wait for the first completed interviews to get a first indication of how long it takes. As soon as you have a first version of your questionnaire, SurveyLength can estimate its length — so you don’t have to adapt it, delete questions and test again until you reach the desired length.