[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.

 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.
```