Defining Formulas (Sample Statistic)
Comment Why is called a sample standard deviation? First, it is computed from sample data. Then why do we use the word standard in the name? We know is a measure of deviation or risk. You should be aware that there are other statistical measures of risk that we have not yet mentioned. However, is the one that everyone uses, so it is called the “standard” (like standard time).
In statistics, the sample standard deviation and sample variance are used to describe the spread of data about the mean . The next example shows how to find these quantities by using the defining formulas. Guided Exercise 3 shows how to use the computation formulas.
As you will discover, for “hand” calculations, the computation formulas for and are much easier to use. However, the defining formulas for and emphasize the fact that the variance and standard deviation are based on the differences between each data value and the mean.