How to write good survey scale questions
Survey scale questions are useful because not only do they tell you what people think, but they also show you answers in relation to each other.
This means that you can compare single answers, or groups of answers. The options for grouping answers means that you can see how groups of respondents (say, by demographics like age, gender, or location) think about what you’ve asked.
Scale questions do all of this in one simple question. This means that when you use them, you are potentially reducing the length of your survey.
It also means you really want to get them right.
How many options is ideal for a survey scale question?
Odd-numbered scales are the best to use, because they have an even number of options either side of the middle. If you were to create a four-option scale, it would look odd and not seem quite right.
The other benefit of an odd-numbered scale is that it allows you to add a neutral option. If you remember our article about writing good survey questions, you’ll know that giving people ‘wriggle room’ is a good idea.
Use a 5-point scale if you’re pretty sure that responses will be fairly evenly positive or negative.
Use a 7-point scale if you suspect responses will cluster towards one end or the other.
Consider including a “Don’t Know” option
In addition to the 5 points or 7 points on these scales, a “Don’t Know” or “Prefer not to answer” option can be important. Rather than forcing respondents to provide an answer, this additional scale still provides an odd number scale and a neutral score along with an option for people who may not have enough information about the survey area to say so.
Even-numbered questions force answers to be positive or negative
You might find it surprising to learn that scales that force a negative or a positive answer can be frustrating to respondents. It’s because they can make them feel like they aren’t able to properly represent how they feel.
This also means that it may damage the data you receive.
If you’re not sure which type of question is best, ask two very similar questions, but each with a different scale. Then, when you test it before you launch, you’ll have a better understanding as to which question should be kept. When you compare the results, you will find that the results are comparable, if not identical.
Can a scale be too long?
The human memory has trouble with too many options, and many usability researchers talk about the 7 +/- 2 rule. This means that the optimum number of options to stop people from being overwhelmed is 7 (plus or minus 2). Theoretically, this means that the maximum number of options you should use is 9.
Realistically, if you agree with something, then deciding how many shades of agreement fits best can be tiring. Too many options can wear people out; and if you do that too often, your abandonment rates will rise.
Survey scale questions: Overview
The best survey scale question give a full set of options, within the most relevant length. It will make the data you get more accurate, and keep completion times low.
Here is a quick-reference guide for the length and outcomes of survey scales:
- 4-point scales: Result in inaccurate data
- 5-point scales: Result in accurate data, and meets needs most of the time
- 7-point scales: Highly accurate results, but most useful for data that is weighted either positive or negative
- 9-point scales: Result in accurate data, but be wary of them because they can tire people out.
- 10-point scales: Tiring questions without a neutral option; avoid them whenever possible.