What do you call the square root of the sample variance?

The square root of the sample variance is referred to as the sample standard deviation. This term is frequently used in statistics to provide a measure of dispersion or spread within a sample data set. The sample variance itself is calculated by taking the average of the squared differences between each data point and the sample mean. When you take the square root of this value, you are converting it back to the original units of measurement for the data, which allows for a more intuitive understanding of variability.

In contrast, the mean is a measure of central tendency and does not reflect variability. Sample variance, while related, represents the squared measures of spread and is not the final step in determining standard deviation. The median, on the other hand, is another measure of central tendency, specifically the middle value of a data set when ordered, and is unrelated to variance or its square root. Thus, the use of the term "sample standard deviation" is appropriate and denotes the square root of the sample variance accurately.