When you get right down to it, there are two purposes of a survey scale question: learn what people think and distribute answers along a continuum.
The second part allows us to compare answers individually (response A versus response B) or as a group (25 year-old buyers versus 20 year-olds).
Using scale questions that offer a complete spectrum of options lets respondents give their true opinions while reducing the length of the survey, so it’s important to get these survey questions right.
To make sure you’re asking the right questions in the right way, we’re going to investigate the pros and cons of various scale lengths and sizes.
Ideal Length for Scale Questions: 5 or 7 Options
For the best data, we recommend using an odd-numbered scale. This allows respondents to select a neutral option and gives a reasonable number of choices on both the positive and negative sides of the scale.
If you expect your results to be fairly equitable, meaning fairly equal numbers of positive and negative responses, then a 5-point scale will be your best bet.
If, on the other hand, you suspect that you’ll be getting responses that skew to one end of the spectrum or the other, you should opt for the 7-point scale.
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The Trouble With Even-Numbered Scale Questions
It can be tempting to create scale questions with an even number of responses like the one below, because these force survey takers to choose either a positive or negative answer.
But while these kinds of questions can actually impoverish your survey data by forcing people who are truly neutral or undecided to arbitrarily choose a side.
This can be frustrating to a respondent who doesn’t feel that their input is being accurately represented, and it can be detrimental to the survey’s accuracy as well.
If you’re skeptical about the impact of using only odd-numbered scale questions, there’s a simple way to test them. Ask the same question in two different parts of your survey, once using an odd-numbered sale and once using an even-numbered scale. Compare the answers, and you’ll almost certainly find that the results are comparable if not statistically identical.
Scale Question Length: How Long is Too Long?
There’s a reason that telephone numbers are only seven digits long. The human mind can easily process approximately seven data bits before it gets overwhelmed and has trouble remembering.
In survey questions, this means that we need to limit the number of scale options to seven or fewer, otherwise respondents will struggle to process the scale itself.
More than seven levels of agreement cannot be considered at once, which makes it difficult to respond to scales with more than seven levels. In short, they are very fatiguing. They deprive the mind of the chance to embrace the scale as one and accurately make a selection from an array of balanced alternatives.
What the mind does with a ten-point scale, for example, is first split it into a positive and negative half. This goes back to the issue with even-numbered scales: the even split makes it frustrating for respondents who want a neutral option.
Scale Question Summary
In sum, using scales that provide a full array of alternatives within an appropriate length permits respondents to complete your survey in a shorter amount of time and with greater accuracy.
4-point scales: an impoverished an inaccurate data set
5-point scales: accurate, and meets your needs 90% of the time
7-point scales: accurate, and more useful for data that skews positive or negative
10-point scales: very fatiguing, and should be avoided at all times