SUBROUTINE POINT

PURPOSE
   TO COMPUTE THE POINT-BISERIAL CORRELATION COEFFICIENT
   BETWEEN TWO VARIABLES, WHEN ONE OF THE VARIABLES IS A BINARY
   VARIABLE AND ONE IS CONTINUOUS.  THIS IS A SPECIAL CASE OF
   THE PEARSON PRODUCT-MOMENT CORRELATION COEFFICIENT.

USAGE
   CALL POINT (N,A,B,HI,ANS,IER)

DESCRIPTION OF PARAMETERS
   N   - NUMBER OF OBSERVATIONS
   A   - INPUT VECTOR OF LENGTH N CONTAINING THE CONTINUOUS
	 VARIABLE
   B   - INPUT VECTOR OF LENGTH N CONTAINING THE DICHOTOMOUS
	 (BINARY) VARIABLE
   HI  - INPUT NUMERICAL CODE TO INDICATE THE HIGHER CATEGORY.
	 ANY VALUE OF THE BINARY VARIABLE NOT LESS THAN HI WILL
	 BE CLASSIFIED IN THE HIGHER OF THE TWO CATEGORIES.
   ANS - OUTPUT VECTOR OF LENGTH 9 CONTAINING THE FOLLOWING
	 RESULTS
	    ANS(1)- MEAN OF VARIABLE A
	    ANS(2)- STANDARD DEVIATION OF VARIABLE A
	    ANS(3)- NUMBER OF OBSERVATIONS IN THE HIGHER
		    CATEGORY OF VARIABLE B
	    ANS(4)- NUMBER OF OBSERVATIONS IN THE LOWER
		    CATEGORY OF VARIABLE B
	    ANS(5)- MEAN OF VARIABLE A FOR ONLY THOSE
		    OBSERVATIONS IN THE HIGHER CATEGORY OF
		    VARIABLE B
	    ANS(6)- MEAN OF VARIABLE A FOR ONLY THOSE
		    OBSERVATIONS IN THE LOWER CATEGORY OF
		    VARIABLE B
	    ANS(7)- POINT-BISERIAL CORRELATION COEFFICIENT
	    ANS(8)- T-TEST FOR THE SIGNIFICANCE OF THE
		    DIFFERENCE BETWEEN THE MEANS OF VARIABLE A
		    FOR THE HIGHER AND LOWER CATEGORIES
		    RESPECTIVELY.
	    ANS(9)- DEGREES OF FREEDOM FOR THE T-TEST
   IER- 1, IF ALL ELEMENTS OF B ARE NOT LESS THAN HI.
	-1, IF ALL ELEMENTS OF B ARE LESS THAN HI.
	0, OTHERWISE.  IF IER IS NON-ZERO, ANS(I), I=5,...,9,
	IS SET TO 10**75.

REMARKS
   THE SYMBOLS USED TO IDENTFY THE VALUES OF THE TWO CATEGORIES
   OF VARIABLE B MUST BE NUMERIC.  ALPHABETIC OR SPECIAL
   CHARACTERS CANNOT BE USED.
   THE T-TEST(ANS(8)) IS A TEST OF WHETHER THE POINT-BISERIAL
   COEFFICIENT DIFFERS SIGNIFICANTLY FROM ZERO.

SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
   NONE

METHOD
   REFER TO P. HORST, 'PSYCHOLOGICAL MEASUREMENT AND
   PREDICTION', P. 91 (WADSWORTH, 1966).