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What is the Optimal Number of Questions for a Mobile Survey?

It’s a question many businesses have when designing mobile surveys: just how many questions should our survey include?

Regardless of the survey’s purpose, a fine balance needs to be struck between having enough questions to obtain all the required information to achieve your objectives – while keeping it succinct enough to complete in one sitting. Too few questions and you could miss out on a great opportunity to gather insight, and thus get minimal return on your survey investment. Too many questions, however, can be just as detrimental, with respondents dropping out if the survey takes too long to finish.

In this edition of Mobile Matters, we take a look at how people’s attention spans are getting shorter with the rise of mobile technology. We then discuss what this means for survey length, and finally, describe what research suggests is the right number of questions for your mobile survey to contain.

Our attention spans are getting shorter

Various sources of recent research seem to point to one conclusion: the proliferation of media channels and mobile devices demanding people’s attention makes it more difficult for people to pay attention for sustained periods.

In fact, competition for eyeballs has become so intense that the National Center for Biotechnology Information believes our attention spans have become worse than those of goldfish – long the subject of ridicule for their poor memory. The Center found that the average human attention span in 2013 was 8 seconds, down from 12 seconds in 2000. In addition, it was revealed that almost one in five (17 per cent) of web page views lasted less than four seconds.

(As an aside, the attention span of goldfish was recorded at a relatively impressive 9 seconds!)

There’s no doubt that the growth of mobile devices has contributed at least in part to our shifting media consumption habits, and thus our attention spans decreasing. A study by OMD found that people switch their attention between devices – such as smartphones, tablets and laptops – an average of 21 times in a single hour.

This obviously has massive implications for mobile surveys. If a survey has too many questions and is taking too long to complete, respondents are more likely to become fatigued and frustrated, perhaps even rushing through their answers (which obviously impacts the quality of the data).  Remember too that other sources of distraction such as laptops, tablets and televisions are often within close viewing distance. Furthermore, mobiles by their very nature are often used by people on the move, hence their ability to devote extended lengths of time to survey completion is often limited.

It is therefore crucial to optimise your mobile survey length to suit the attention span of respondents to ensure good response rates.

How long does it take to answer a mobile survey?

According to recent research, it takes an average respondent approximately 20 seconds to read, process and answer a single question. While some people will take less or more time, the implication is that it takes an average of a full minute to take care of just three standard questions.

Further studies found that the average time spent per question decreases as the number of questions goes up. For a survey with between 11 and 15 questions, respondents spend 25 seconds per question, taking a total of 2 to 5 minutes to complete the entire survey.

So clearly, it’s crucial that your surveys are the right length to maximise user engagement and response rates.

So just how many questions is appropriate for a mobile survey?

15 is the magic number for mobile surveys

Based on feedback from over 9 million surveys, On Device Research recommends that 15 questions is the optimal number for mobile questionnaires.

Despite the beliefs many people hold over keeping a mobile survey as short as possible, On Device Research suggests that a 15-question survey is succinct enough to complete without much fuss. Anything longer than that, however, is pushing it – with each question beyond the 15 mark slashing the response rate by 5 to 10 per cent.

When developing your next survey, you should therefore always aim to keep this number in mind. Use techniques like preloading data into your survey, branching and hiding questions and incorporating substitution values into the questions so that the respondent is kept engaged and only shown the questions relevant to them. These are all clever tools approaches you can use to keep your mobile survey to the 15 questions, so you can achieve the right balance between collecting sufficient and meaningful data while keeping the survey short enough for people to complete.

Happy surveying!

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