PStDev (Tag-based PE function)

Returns the population standard deviation for a population of two or more values.

Syntax

PStDev(x1, x2, ..., xn)

Arguments

x1...xn

May be numbers or time expressions, but all must be the same.

Returns

The population standard deviation for the arguments. For numerical arguments the result is a number. For arguments that are time expressions (absolute times or time periods), the result is a number indicating a time period expressed in seconds.

The population standard deviation of a population x1...xn is

where is the mean of the arguments; that is,

Exceptions

Arguments whose run-time values are digital states are ignored. If all values are digital states, an error value is returned.

Notes

PStDev uses every value in a population to calculate the population standard deviation. However, it is common, especially for a large population, to estimate standard deviation from a sample of the population. SStDev uses a set of sample values to calculate sample standard deviation, which approximates the population standard deviation.

Example

PStDev('att1', 'att2')

PStDev('*','14-Dec-97', 'y')

PStDev('*'-'y','14-Dec-97'-'*', '-1h')