[Overview][Constants][Types][Classes][Procedures and functions][Index] | Reference for unit 'Math' (#rtl)

# StdDev

Return standard deviation of data

## Declaration

Source position: math.pp line 518

`function StdDev(`
`const data: array of Single`
`):Float; function StdDev(`
`const data: PSingle;`
`const N: Integer`
`):Float; function StdDev(`
`const data: array of Double`
`):Float; function StdDev(`
`const data: PDouble;`
`const N: Integer`
`):Float; function StdDev(`
`const data: array of Extended`
`):Float; function StdDev(`
`const data: PExtended;`
`const N: Integer`
`):Float;`

## Description

Stddev returns the standard deviation of the values in Data. It returns zero if there is only one value.

The second form of the function accepts a pointer to an array of N values.

## Errors

None.

## See also

mean |  | Return mean value of array
meanandstddev |  | Return mean and standard deviation of array
variance |  | Return variance of values
totalvariance |  | Return total variance of values

## Example

    Program Example40;

    { Program to demonstrate the stddev function. }
    { @ should return typed pointer }
    {$T+}

    Uses Math;

    Var
      I : Integer;
      ExArray : Array[1..10000] of Float;

    begin
      Randomize;
      for I:=low(ExArray) to high(ExArray) do
        ExArray[i]:=Randg(1,0.2);
      Writeln('StdDev     : ',StdDev(ExArray):8:4);
      Writeln('StdDev (b) : ',StdDev(@ExArray[1],10000):8:4);
    end.