# How do you do Standard Deviation??

Relevance

First find the mean (average). Then subtract each data number from the mean, and square the difference. Add up all these squared differences and find the average of that sum. Then take the square root of that average. That's the standard deviation.

• Login to reply the answers
• robertspr... and hayharbr are both right. Both of these are correct for different situations.

You divide by n when you have the entire population. That's just the measure of spread for the population.

You divide by n-1 when you have a sample, because you're generally using it to estimate the population standard deviation. The n-1 makes it so that, on average, your estimate will be correct.

• Login to reply the answers
• hayharbr is right except the average is the sum divided by n. For standard deviation you should devide the sum by n-1. The difference is very slight except in very small samples.

• Login to reply the answers
• Are you in my math class because we're doing the same thing right now! haha

• Login to reply the answers
• Login to reply the answers
• Login to reply the answers
• Login to reply the answers