FUNCTION PFT(ID,M,N,X)
C WAHRSCHEINLICHKEIT VON F(M,N)=X UND T(N)=X
C FUER ID=0 :  FISHER'S F-WERT  :  PFT(O,M,N,X)
C   "  ID=1 : STUDENT'S T-WERT  :  PFT(1,1,N,X)
C FREIHEITSGRADE M,N  -  NACH DECUS NO. FOCAL8-308
C FORTRAN II
	X=X+.1E-15
	IF(ID)1001,1001,1000
1000	X=X**2
1001	IA=2*(M/2)-M+2
	IB=2*(N/2)-N+2
	W=X*FLOAT(M)/FLOAT(N)
	Z=1./(1.+W)
	IF(IA-1)1003,1003,1002
1002	IF(IB-1)1004,1005,1004
1004	D=Z**2
	P=W*Z
	GOTO 1010
1005	P=SQRT(Z)
	D=.5*Z*P
	P=1.-P
	GOTO 1010
1003	IF(IB-1)1006,1007,1006
1006	P=SQRT(W*Z)
	D=.5*P*Z/W
	GOTO 1010
1007	P=SQRT(W)
	Y=.31830989
	D=Y*Z/P
	P=2.*Y*ATAN(P)
1010	Y=2.*W/Z
	J=IB+2
1016	IF(J-N)1008,1008,1015
1008	D=(1.+FLOAT(IA)/(FLOAT(J-2)))*D*Z
	IF(IA-1)1009,1011,1009
1009	P=(P+W)*Z
1012	J=J+2
	GOTO 1016
1011	P=P+D*Y/FLOAT(J-1)
	GOTO 1012
1015	Y=W*Z
	Z=2./Z
	IB=N-2
	I=IA+2
1017	IF(I-M)1020,1020,1025
1020	J=I+IB
	D=Y*D*FLOAT(J)/FLOAT(I-2)
	P=P-Z*D/FLOAT(J)
	I=I+2
	GOTO 1017
1025	PFT=1.-P
	RETURN
	END