# How to calculate relative deviation

Written by vanessa padgalskas
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The relative deviation or relative standard deviation is another way of expressing the standard deviation. Standard deviation measures how accurate the average is by calculating random error, which cannot be controlled. The relative deviation expresses the standard deviation as a per cent.

Skill level:
Easy

### Things you need

• Average
• Standard Deviation
• Calculator

## Instructions

1. 1

Calculate the average for your group of numbers. The formula for the average is: average = (X1 + X2 + X3 ....) / n where "n" equals the total number of x values.

2. 2

Calculate the standard deviation. To find the standard deviation you take the square root of [ (X1 - average)^2 + (X2 - average)^2 .... / (n - 1)] Refer to the link under "References" for the equation written mathematically.

3. 3

Calculate relative standard deviation by diving the standard deviation by the average then multiply by 100. Your answer will be expressed as a percentage.

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