What’s the optimal length for a mobile survey?

on Monday July 15, 2013 @ 12:08

Ideal length of the survey on a mobile is one of the most frequently asked question and for a good reason – there’s a well justified fear that mobile requires a super short survey. Not entirely true.

We’ve done over 9 million surveys to date and learned quite a lot in terms of the optimal number of questions and answer options. 

15 questions is enough

While we advise to ask as few questions as possible (but as many as necessary) the recommendation is to stop at 15. To many this is a surprisingly high number of questions as the conventional thinking goes that people lose interest quicker on a smaller screen. Mobile surveys can be fairly long without seeing much drop-off in completes.

Every question beyond 15 cuts response rate by 5-10%.

Keeping your survey shorter, using routing to ask more questions only from a sub-set of the respondents is recommended. Add more questions only if you absolutely have to and your audience is large enough to compensate for the higher drop-off rate.

Long questions are killers

Twitter is onto something with it’s 140 character limit. After a respondent is exposed to a long questions, the average UK drop-off rate increases +4.8%, in India 6% versus a shorter question. This drop-off can be even more dramatic further into the survey (after the 10th question) as people start losing interest.

It’s not only about the length either – use simple everyday language to make the question easy to understand. In the battle of “do they understand it?” vs. “is it 100% scientific” we’d vote for the former. Consider your audiences, their education level, proficiency with language – and then try to cut your question length by further 25% – any copywriter will tell you – shorter is better.

How many answer options?

Too long list of answers has the same effect as having too long and complicated question – people close your finely crafted survey and go check out their friends status updates on Facebook.

10 is really the maximum number of answers you should have per questions. More choices than that and you’ll lose around 5% of respondents. If it’s a mandatory question then it’s game over, the person answering will quit the whole survey.

What is the frequency of your automotive travel to your parents’ residents in the last 30 days?

If you find yourself wanting to add more choice then step back and see if you can split the question up into several questions instead. Trying to fit all answers on one mobile screen is not a hard rule. However, a long list of options increases the cognitive load on someone who might be answering your survey during a commute, commercial break between their favorite TV show or while being pulled along by their eager dog their walking.

Test it before sending it

It’a hard to see your survey with fresh eyes so simply ask a friend, colleague or family member to take the survey and give you feedback.

They’ll have to take it on a mobile to mimic real respondents as much as possible and give them space to take it. Borrow a lesson from user testing – with 3 people taking your survey you’ll unearth the 2 biggest flaws with the questions, answer options and overall flow.

Join our Newsletter