## Trending News

# How do you do Standard Deviation??

### 7 Answers

- hayharbrLv 71 decade agoFavorite Answer
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

- 1 decade ago
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

- robertspraguejrLv 41 decade ago
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

- 1 decade ago
Are you in my math class because we're doing the same thing right now! haha

- Login to reply the answers

- How do you think about the answers? You can sign in to vote the answer.
- 1 decade ago
If you have a scientific calendar, it should tell you in the instructions.

- Login to reply the answers