Microsoft Office Tutorials and References
In Depth Information
Using sample and population statistical functions
Using sample and population statistical functions
Variance and standard deviation are statistical measurements of the dispersion of a group,
or population, of values. The standard deviation is the square root of the variance. As a rule,
about 68 percent of a normally distributed population falls within one standard deviation
of the mean, and about 95 percent falls within two standard deviations. A large standard
deviation indicates that the population is widely dispersed from the mean; a small standard
deviation indicates that the population is tightly packed around the mean.
The VAR and STDEV function families compute the variance and standard deviation of
the numbers in a range of cells. Before you make these calculations, you must determine
whether those values represent the total population or only a representative sample of
that population. The VAR.S and STDEV.S functions assume that the values represent only a
sample of the total population, while the VAR.P and STDEV.P functions assume that the
values represent the total population. The A versions—VARA, VARPA, STDEVA, and STDEVPA—
include numeric text entries and logical values in their calculations, while the others do not.
Calculating sample statistics: VAR.S and STDEV.S
The VAR.S and STDEV.S functions compute variance and standard deviation, assuming that
their arguments represent only a sample of the total population. These functions take the
arguments number1 , number2 , and so on, and they accept up to 255 arguments. The
worksheet in Figure 17-2 shows exam scores for five students and assumes that the scores in
cells B4:E8 represent only a part of the total population.
Figure 17-2 Here, the VAR.S and STDEV.S functions measure the dispersion of sample exam
scores.
You can find the VAR.xlsx file with the other examples on the companion website.
The formula in cell I4 =VAR.S(B4:E8) calculates the variance for this sample group of test
scores. The formula in cell I5 =STDEV.S(B4:E8) calculates the standard deviation.
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