Find the standard deviation of a data set, both sample and population, with the mean. Enter the numbers separated by commas.
Usage Tip
Use sample standard deviation (n − 1) unless your data is the entire population — it is the common default in statistics.
Sample divides by n − 1; population divides by n
The sample version (n − 1) corrects for estimating from a sample; the population version (n) is for complete data.
Sample SD is the default; population SD is shown alongside.
About 68 percent of normal data falls within one SD of the mean.
Standard deviation describes how spread out the values in a data set are around the mean. A small standard deviation means the values cluster close to the average, while a large one means they are widely scattered. It is the square root of the variance, so it is in the same units as the data.
The sample version divides by one less than the number of values and is the one to use when your data is only a part of a larger group, while the population version divides by the total count and applies when you have every value. In a roughly bell shaped data set, about 68 percent of values fall within one standard deviation of the mean and 95 percent within two. Check for outliers, since a single extreme value can raise the standard deviation a lot.