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PHI.FOR
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1985-12-31
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123 lines
C
C ..................................................................
C
C SUBROUTINE PHI
C
C PURPOSE
C TO COMPUTE THE PHI COEFFICIENT BETWEEN TWO VARIABLES WHICH
C ARE DICHOTOMOUS.
C
C USAGE
C CALL PHI (N,U,V,HU,HV,P,CH,XP,IE)
C
C DESCRIPTION OF PARAMETERS
C N - NUMBER OF OBSERVATIONS
C U - INPUT VECTOR OF LENGTH N CONTAINING THE FIRST DICHOTO-
C MOUS VARIABLE
C V - INPUT VECTOR OF LENGTH N CONTAINING THE SECOND DICHOTO-
C MOUS VARIABLE
C HU - INPUT NUMERICAL CODE WHICH INDICATES THE HIGHER
C CATEGORY OF THE FIRST VARIABLE. ANY OBSERVATION IN
C VECTOR U WHICH HAS A VALUE EQUAL TO OR GREATER THAN HU
C WILL BE CLASSIFIED IN THE HIGHER CATEGORY.
C HV - INPUT NUMERICAL CODE FOR VECTOR V, SIMILAR TO HU
C P - PHI COEFFICIENT COMPUTED
C CH - CHI-SQUARE COMPUTED AS A FUNCTION OF PHI COEFFICIENT
C (DEGREES OF FREEDOM FOR CHI-SQUARE = 1)
C XP - COMPUTED VALUE OF THE MAXIMAL PHI COEFFICIENT THAT
C CAN BE ATTAINED IN THE PROBLEM
C IE - IF IE IS NON-ZERO, SOME CELL IN THE 2 BY 2 TABLE IS
C NULL. IF SO, P, CH, AND XP ARE SET TO 10**75.
C
C REMARKS
C VARIABLES U AND V MUST BE SPECIFIED NUMERIC.
C THE PHI COEFFICIENT IS A SPECIAL CASE OF THE
C PEARSON PRODUCT-MOMENT CORRELATION WHEN BOTH VARIABLES ARE
C BINARY.
C
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
C NONE
C
C METHOD
C REFER TO P. HORST, 'PYSCHOLOGICAL MEASUREMENT AND
C PREDICTION', P. 94 (WADSWORTH, 1966).
C
C ..................................................................
C
SUBROUTINE PHI (N,U,V,HU,HV,P,CH,XP,IE)
C
DIMENSION U(1),V(1)
C
C CONSTRUCT A 2X2 CONTINGENCY TABLE
C
IE=0
A=0.0
B=0.0
C=0.0
D=0.0
C
DO 40 I=1,N
IF(U(I)-HU) 10,25,25
10 IF(V(I)-HV) 15,20,20
15 D=D+1.0
GO TO 40
20 B=B+1.0
GO TO 40
25 IF(V(I)-HV) 30,35,35
30 C=C+1.0
GO TO 40
35 A=A+1.0
40 CONTINUE
IF(A) 100,100,41
41 IF(B) 100,100,42
42 IF(C) 100,100,43
43 IF(D) 100,100,44
C
C COMPUTE THE PHI COEFFICIENT
C
44 P=(A*D-B*C)/ SQRT((A+B)*(C+D)*(A+C)*(B+D))
C
C COMPUTE CHI-SQURE
C
T=N
CH=T*P*P
C
C COMPUTE THE MAXIMAL PHI COEFFICIENT
C
P1=(A+C)/T
P2=(B+D)/T
P3=(A+B)/T
P4=(C+D)/T
IF(P1-P2) 75, 45, 45
45 IF(P3-P4) 65, 50, 50
50 IF(P1-P3) 60, 55, 55
55 XP=SQRT((P3/P4)*(P2/P1))
GO TO 95
60 XP=SQRT((P1/P2)*(P4/P3))
GO TO 95
65 IF(P1-P4) 70, 55, 55
70 XP=SQRT((P2/P1)*(P3/P4))
GO TO 95
75 IF(P3-P4) 90, 80, 80
80 IF(P2-P3) 60, 85, 85
85 XP=SQRT((P4/P3)*(P1/P2))
GO TO 95
90 IF(P2-P4) 70, 85, 85
C
95 RETURN
100 IE=1
P=1.E38
CH=1.E38
XP=1.E38
GO TO 95
END
T((P2/P1)*(P3/P4))
GO TO 95
75 IF(P3-P4) 90, 80,