There's a long-running debate about customer service survey rating scales.

Some people think they should be even, such as a survey that asks customers to rate their satisfaction on a scale of 1-4.

Others think survey scales should be odd, making the customer satisfaction scale go from 1-5.

Let's take a look at both arguments where you'll see there's one clear answer.

The Case for Even Rating Scales

Proponents of an even survey scale argue this design forces customers to choose a positive or negative response.

There's no room for wishy-washy, neutral ratings. A customer is either satisfied or unsatisfied. Here's how that breaks down on a 1-4 scale:

Some people might even point to the simplicity of the thumbs up, thumbs down rating scales that many surveys now use. Even Netflix recently ditched its five star rating system in favor of this one. 

There's a glaring hole in this argument: bias. 

A good survey shouldn't lead customers to one answer or another. It should allow customers to give their actual response, even if its neutral. The whole argument for even scales is making customers adjust their rating.

This is why even scales made my list of nine underhanded ways to boost your survey scores.

The Case for Odd Rating Scales

This argument is based on math.

An odd-numbered scale contains a statistical mid-point. Here's how that breaks down on a 1-5 scale:

The neutral mid-point is the reason the creators of the Net Promoter Score (NPS) advocate a scale of 0-10 rather than 1-10. It's also the reason the inventors of the Customer Effort Score (CES) advocate a scale of 1-7 instead of 1-6 or 1-8.

Conclusion

A good customer service survey starts with a clear purpose.

Are you doing a survey to get actionable feedback or are you just trying to make your scores look good? My advice is to stick with an odd-numbered rating scale if you want unbiased customer feedback that will help you improve your company's customer service.