What is the 90th percentile and how to calculate 90th percentile?

Before explaining the 90th percentile let’s see what is percentile. A percentile is a measure used in statistics indicating the value below which a given percentage of observations in a group of observations fall.

For example the 30th percentile is the value below which 30 percent of the observations may be found.

In similar way the 90th percentile is the value below which 90 percent of the observations may be found.

How to calculated 90^th percentile?

Click here to know more

As we know it is the value from which 90% of the samples are smaller so let’s find the 90^th percentile in simple easy steps.

Step 1: Sort the values in increasing order.

Step 2: Eliminate the top 10% values.

Step 3: The highest value you are left with is the 90^th percentile.

Example:

Suppose we have following sample of data: 1, 5, 3, 9, 4, 7, 7, 9, 11, and 21.

Sorting the data in ascending order gives: 1, 3, 4, 5, 7, 7, 9, 11 and 21.

After removing top 10% values (10% of 10 = 1) we have 1, 3, 4, 5, 7, 7, 9 and 11.

The 90^th percentile is 11.

What is the significance of 90^th percentile?

It answers the following questions:

1. What percentage of transactions have a response time less than or equal to X seconds?

2. What is the time under which 90 percent of the transactions are responding?