# How do you calculate 3 SD?

Feb 27, 2021

## How do you calculate 3 SD?

An Example of Calculating Three-Sigma LimitFirst, calculate the average of the observed data. Second, calculate the variance of the set. Third, calculate the standard deviation, which is simply the square root of the variance. Fourth, calculate three-sigma, which is three standard deviations above the mean.

What is 3 standard deviations from the mean?

99.7%

What percentage is 3 sigma?

99.7 percent

### How much is 3 standard deviations?

Three standard deviations account for 99.7% of the sample population being studied, assuming the distribution is normal or bell-shaped (see the 7 rule, or the empirical rule, for more information).

What is 4 standard deviations from the mean?

95% of the population is within 2 standard deviations of the mean. 99% of the population is within 2 1/2 standard deviations of the mean. 99.7% of the population is within 3 standard deviations of the mean. 99.9% of the population is within 4 standard deviations of the mean.