How much better? {Simple Stat: Percentage Better}

Have you ever tried to figure out how much something about your business has improved? Have you been taking surveys and collecting data but don't really know how to analyze it? This is a math lesson about how to calculate percentage of improvement.

Creative Commons licensed photo by flickr.com user James Cridland.

As an example, let's pretend that you have been trying to improve overall customer satisfaction, and you've been conducting surveys for the past year. On a 5-point scale, you received these averages from customer surveys for overall satisfaction:

Q1	Q2	Q3	Q4
3.5	3.8	4.3	4.8

How do you calculate percentage of improvement?
To calculate quarter-to-quarter improvement, you will compare each quarter. So, from the first to second quarter, follow these steps:

1. Subtract the Q2 value from the Q1 value (Q2-Q1=difference):

 3.8-3.5=.3 difference.

As a raw figure, this doesn’t seem that great, does it?

2. Divide the difference by the Q1 value (Difference/3.5=raw score):

Divide .3 by 3.5 = .0857 to get a raw score

3. Multiply the raw score by 100 to determine the percentage of improvement
(Raw score * 100=percentage of improvement):

.0857 x 100 =8.57

In plain English, this means service has improved 8.6%.

At the end of the year, you can calculate the overall improvement for the year by plugging in the Q1 and Q4 numbers, like this:

4.8-3.5=1.3
1.3 /3.5=.3714
.3714 x 100 =37.14

Or, over the three quarters, service improved 37%.

If you want to skip the math, try an online percentage improvement calculator.

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