4.1.3.2.7 StandardError

StandardError function

Prototype:	function StandardError (const StandardDeviation :extended; const NSample :integer) : extended;
Description:	Calculates standard error of variable with specified number of observations and standard deviation
Syntax:	variable := StandardError (StandardDeviation, NSample);
	Part	Description
	variable	A variable declared as type of extended
	StandardDeviation	Sample standard deviation
	NSample	Number of observations in sample


Return value:	Standard error
Definition:	Standard deviation / (Number of observations ^ 0.5)

Example:

Task:

Calculate standard error of DBH.

Data stored in the database.

Script:

var

tab : TTableWrapper;

attributeName: string;

nullAsZero: boolean;

x,e: extended;

begin

tab:= Trees.table;

attributeName:= 'DBH_mm';

nullAsZero:= false; // dont want calculate with a null value

x:= StandardDeviation(tab, attributeName, nullAsZero);

e:= StandardError(x, Trees.RecordCount); // Trees.RecordCount returns number of records

//e:= StandardError(StandardDeviation(tab, attributeName, nullAsZero), Trees.RecordCount); //this is same as previous line

ShowMessage(FloatToStr(e));

end.

Output in Field-Map Data Collector:

standard error of DBH