People are frequently asked to rate something on a scale of 1 to 10. Let’s take the pain Numeric Rating Scale (NRS-11) as an example. 1 means low pain (bump), 10 means extreme pain (migraine). Now what would warrant a 2 or a 9? A person simply can’t categorize pain into 10 different levels. The  NRS-11 groups the 10 pain levels into 3 categories (Mild, Moderate, Severe). Why not just use a 3-point scale or the category names?

I postulate that most 10-point scales can be replaced with 5-point scales with no loss of information. For analysis purposes, most responses are going to be grouped into 3 – 5 categories or averaged.

Conversion of existing 10-point data values to 5-point data values is easy.

1. Add 1 to the 10-point value
2. Divide the result by 2
3. Drop the fractional part

Example for value 9:

1. 9 + 1 = 10
2. 10 / 2 = 5

Example for value 10:

1. 10 + 1 = 11
2. 11 / 2 = 5.5
3. Drop the .5 = 5