If the data represents the entire population, you’ve got the option to use theSTDEV.P function.
Both functions are fully automatic.
results are accurate because all data is available.
However, when you calculate statistics for a sample, results are estimates and therefore not as accurate.
Bessel’s correctionis an adjustment made to correct for bias that happens when working with sample data.
It appears in formulas as n-1, where n is the count.
When working with a sample population, Bessel’s correction can provide a better estimation of the standard deviation.
Remember that a small sample is not likely to be a good approximation of a population in most cases.
On the other hand, a large enough sample size will approach the statistics produced for a population.
In these cases, Bessels correction may not be useful.
Manual calculations for standard deviation
The screen below shows how to manually calculate standard deviation in Excel.
Column D calculates Deviation, which the value minus mean.
The formula in D5, copied down is:
Column E shows deviations squared.
STDEV.P calculates standard deviation using the “n” method, ignoring logical values and text.
STDEV.S Function
The Excel STDEV.S function calculates the standard deviation for a sample set of data.
STDEV.S replaces the older STDEV function, with the same behavior.
STDEV Function
The Excel STDEV function returns the standard deviation for data that represents a sample.
To calculate the standard deviation for an entire population, use STDEVP or STDEV.P.
STDEVP Function
The STDEVP function calculates the standard deviation for data that represents a population.
STDEVP has been replaced with a newer function called STDEV.P, which has the same behavior.
