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SIGT.PAS
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Wrap
Pascal/Delphi Source File
|
1985-05-17
|
3KB
|
61 lines
(*-------------------------------------------------------------------------*)
(* Sigt -- Significance of t distribution *)
(*-------------------------------------------------------------------------*)
FUNCTION Sigt( t , Df : REAL ) : REAL;
(*-------------------------------------------------------------------------*)
(* *)
(* Function: Sigt *)
(* *)
(* Purpose: Evaluates t distribution probability ( 2 - tailed ) *)
(* *)
(* Calling Sequence: *)
(* *)
(* P := Sigt( F , Df ); *)
(* *)
(* t --- t-value *)
(* Df --- degrees of freedom *)
(* *)
(* P --- Resultant probability (two-tailed) *)
(* *)
(* Calls: *)
(* *)
(* CdBeta *)
(* *)
(* Method: *)
(* *)
(* The input values are transformed to match the *)
(* requirements of the Beta distribution. Function CDBeta *)
(* provides the corresponding cumulative Beta distribution *)
(* probability. *)
(* *)
(* An error in the input arguments results in a returned *)
(* probability of -1. *)
(* *)
(*-------------------------------------------------------------------------*)
CONST
Dprec = 12;
MaxIter = 200;
VAR
Iter: INTEGER;
Cprec: REAL;
Ifault: INTEGER;
Pval: REAL;
BEGIN (* Sigt *)
Pval := -1.0;
IF( Df > 0.0 ) THEN
BEGIN
Pval := CDBeta( Df / ( Df + t * t ), Df / 2.0, 0.5,
Dprec, MaxIter, Cprec, Iter, Ifault );
IF Ifault <> 0 THEN Pval := -1.0;
END;
Sigt := Pval;
END (* Sigt *);