The worksheet functions VAR.S and VARA calculate the sample variance. The relationship between VAR.S and VARA is the same as the relationship between VAR.P and VARPA. VAR.S ignores cells that contain logical values and text whereas VARA doesn't.
Standard Deviation:
After you calculate the variance of a set of numbers, you have a value whose units are different from your original measurements. For example, if your original measurements are in inches, their variance is in squared inches. This is because you square the deviations before you average them.
Often it's more intuitive if you have a variation statistic that's in the same units as the original measurements. It's easy to turn variance into that kind of statistic, all you have to do is take the square root of variance. This is called standard deviation.
Population Standard Deviation: The standard deviation of a population is the square root of the population variance. For these measurements in inches: 50, 47, 52, 46, and 45, the population variance is 6.8 square inches. The population standard deviation is 2.61 inches.
The Excel worksheet functions STDEV.P and STDEVPA calculate the population standard deviation. STDEV.P ignores blank cells and text whereas STDEVPA takes it into account (blank cells as 0, FALSE as 0, and TRUE as 1).
Sample Standard Deviation:
The standard deviation of a sample, an estimate of the standard deviation of a population, is the square root of the sample variance.
For these measurements 50, 47, 52, 46, and 45 the sample population variance is 8.5 square inches (VAR.S). The sample population standard deviation is 2.92 inches
Excel Functions STDEV.S and STDEVA calculate sample standard deviation. STDEVA uses text and logical values in it's calculations.
No comments:
Post a Comment