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STDEV

Description: Estimates standard deviation based on a sample. Non-numerical values are ignored. The standard deviation is a measure of how widely values are dispersed from the average value (the mean).

Syntax: STDEV(Number1, Number2, ...)

• Number1, Number2, ... are 1 to 30 number arguments corresponding to a sample of a population. You can also use a single array or a reference to an array instead of arguments separated by commas.

Remarks:

• STDEV assumes that its arguments are a sample of the population. If your data represents the entire population, then compute the standard deviation using STDEVP.

• The standard deviation is calculated using the "unbiased" or "n-1" method.

• Arguments can either be numbers or names, arrays or references that contain numbers.

• Logical values and text representations of numbers that you type directly into the list of arguments are counted.

• If an argument is an array or reference, only numbers in that array or reference are counted. Empty cells, logical values, text or error values in the array or reference are ignored.

• Arguments that are error values or text that cannot be translated into numbers cause errors.

• STDEV uses the following formula:

where x is the sample mean AVERAGE(Number1, Number2,…) and n is the sample size.

Example:

Suppose 10 tools stamped from the same machine during a production run are collected as a random sample and measured for breaking strength. The sample values (1345, 1301, 1368, 1322, 1310, 1370, 1318, 1350, 1303, 1299) are stored in A2:E3, respectively. STDEV estimates the standard deviation of breaking strengths for all the tools.

• STDEV(A2:E3) = 27.46