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BISER.FOR
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1985-12-31
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131 lines
C
C ..................................................................
C
C SUBROUTINE BISER
C
C PURPOSE
C TO COMPUTE THE BISERIAL CORRELATION COEFFICIENT BETWEEN TWO
C CONTINUOUS VARIABLES WHEN ONE OF THEM HAS BEEN ARTIFICIALLY
C DICHOTOMIZED.
C
C USAGE
C CALL BISER (N,A,B,HI,ANS,IER)
C
C DESCRIPTION OF PARAMETERS
C N - NUMBER OF OBSERVATIONS
C A - INPUT VECTOR OF LENGTH N CONTAINING THE CONTINUOUS
C VARIABLE
C B - INPUT VECTOR OF LENGTH N CONTAINING THE DICHOTOMIZED
C VARIABLE
C HI - INPUT - NUMERICAL CODE TO INDICATE THE HIGHER CATEGORY
C OF THE DICHOTOMIZED VARIABLE. ANY VALUE IN VECTOR B
C EQUAL TO OR GREATER THAN HI WILL BE CLASSIFIED INTO
C THE HIGHER CATEGORY.
C ANS - OUTPUT VECTOR OF LENGTH 8 CONTAINING THE FOLLOWING
C ANS(1) - MEAN OF VARIABLE A
C ANS(2) - STANDARD DEVIATION OF VARIABLE A
C ANS(3) - PROPORTION OF THE CASES IN THE HIGHER
C CATEGORY OF VARIABLE B
C ANS(4) - PROPORTION OF THE CASES IN THE LOWER
C CATEGORY OF VARIABLE B
C ANS(5) - MEAN OF VARIABLE A FOR THOSE CASES FALLING
C INTO THE HIGHER CATEGORY OF VARIABLE B
C ANS(6) - MEAN OF VARIABLE A FOR THOSE CASES FALLING
C INTO THE LOWER CATEGORY OF VARIABLE B
C ANS(7) - BISERIAL CORRELATION COEFFICIENT
C ANS(8) - STANDARD ERROR OF BISERIAL CORRELATION
C COEFFICIENT
C IER - 1, IF NO CASES ARE IN THE LOWER CATEGORY OF VARIABLE
C B.
C -1, IF ALL CASES ARE IN THE LOWER CATEGORY OF
C VARIABLE B.
C 0, OTHERWISE.
C IF IER IS NON-ZERO, ANS(I)=10**75,I=5,...,8.
C
C REMARKS
C THE VALUES OF THE DICHOTOMIZED VARIABLE, B, MUST BE IN
C NUMERIC FORM. THEY CANNOR BE SPECIFIED BY MEANS OF
C ALPHABETIC OR SPECIAL CHARACTERS.
C
C SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
C NDTRI
C
C METHOD
C REFER TO P. HORST, 'PSYCHOLOGICAL MEASUREMENT AND
C PREDICTION', P.95-96 (WADSWORTH, 1966).
C
C ..................................................................
C
SUBROUTINE BISER (N,A,B,HI,ANS,IER)
C
DIMENSION A(1),B(1),ANS(1)
C
C COMPUTE MEAN AND STANDARD DEVIATION OF VARIABLE A
C
IER=0
SUM=0.0
SUM2=0.0
DO 10 I=1,N
SUM=SUM+A(I)
10 SUM2=SUM2+A(I)*A(I)
FN=N
ANS(1)=SUM/FN
ANS(2)=(SUM2-ANS(1)*SUM)/(FN-1.0)
ANS(2)= SQRT(ANS(2))
C
C FIND PROPORTIONS OF CASES IN THE HIGHER AND LOWER CATEGORIES
C
P=0.0
SUM=0.0
SUM2=0.0
DO 30 I=1,N
IF(B(I)-HI) 20, 25, 25
20 SUM2=SUM2+A(I)
GO TO 30
25 P=P+1.0
SUM=SUM+A(I)
30 CONTINUE
ANS(4)=1.0
ANS(3)=0.0
Q=FN-P
IF (P) 35,35,40
35 IER=-1
GO TO 50
40 ANS(5)=SUM/P
IF (Q) 45,45,60
45 IER=1
ANS(4)=0.0
ANS(3)=1.0
50 DO 55 I=5,8
55 ANS(I)=1.E38
GO TO 65
60 ANS(6)=SUM2/Q
P=P/FN
Q=1.0-P
C
C FIND ORDINATE OF THE NORMAL DISTRIBUTION CURVE AT THE POINT OF
C DIVISION BETWEEN SEGMENTS CONTAINING P AND Q PROPORTIONS
C
CALL NDTRI (Q,X,Y,ER)
C
C COMPUTE THE BISERIAL COEFFICIENT OF CORRELATION
C
R=((ANS(5)-ANS(1))/ANS(2))*(P/Y)
C
C COMPUTE THE STANDARD ERROR OF R
C
ANS(8)=( SQRT(P*Q)/Y-R*R)/SQRT(FN)
C
C STORE RESULTS
C
ANS(3)=P
ANS(4)=Q
ANS(7)=R
C
65 RETURN
END
ANS(6)=SUM2/Q
P=P/FN
Q=1.0-P
C