XTAB
	----

	THE FORTRAN PROGRAM XTAB HAS ALL THE ESSENTIAL FEATURES OF THE
	"XTAB" COMMAND IN THE PROGRAM CROSS BUT OPERATES ON USER-ENTERED
	CONTINGENCY TABLES INSTEAD OF READING DATA FROM A FILE.


      PROGRAM XTAB

      DESCRIPTION
	THIS PROGRAM CROSS-TABULATES PAIRS OF VARIABLES (WITH OR WITHOUT
	A CONTROL VARIABLE) GIVING FREQUENCIES, PERCENTAGES, OR OTHER
	STATISTICS DESIRED BY THE USER.

      SOURCE
	NORMAN W. JOHNSON, DEPARTMENT OF MATHEMATICS, WHEATON COLLEGE,
	NORTON, MASS.

      INSTRUCTIONS
	THE USER MAY ENTER OR ANALYZE DATA BY GIVING ONE OF THE COMMANDS
	"INPUT", "OUTPUT", OR "ZERO" OR MAY TERMINATE THE EXECUTION OF
	THE PROGRAM BY TYPING "STOP".

	THE COMMAND "INPUT" (OPTIONALLY FOLLOWED BY THE TABLE SIZE) EN-
	ABLES THE USER TO ENTER A HYPOTHETICAL FREQUENCY TABLE FOR TWO
	OR THREE VARIABLES TO BE CROSS-TABULATED.  ONE OR MORE OUTPUT
	OPTIONS MUST BE SELECTED AND THE APPROPRIATE CODE NUMBERS EN-
	TERED.  THE FOLLOWING OPTIONS ARE AVAILABLE:

		1--FREQUENCY OF RESPONSES
		2--PERCENTAGES ACROSS
		3--PERCENTAGES DOWN
		4--PERCENTAGES OF TOTAL
		5--CHI-SQUARE, DEGREES OF FREEDOM, AND PROBABILITY
		6--GOODMAN AND KRUSKAL'S TAU
		7--YULE'S Q OR GOODMAN AND KRUSKAL'S GAMMA
		8--PHI COEFFICIENT OR KENDALL'S TAU
		9--SOMER'S D

	THE COMMAND "OUTPUT" PERMITS THE USER TO KEEP THE DATA OF THE
	LAST CROSS-TABULATION BUT TO CHANGE THE OUTPUT OPTIONS.

	THE COMMAND "ZERO", GIVEN AFTER A CROSS-TABULATION INVOLVING A
	CONTROL VARIABLE, PRODUCES THE CORRESPONDING ZERO-ORDER STATIS-
	TICS.

	AFTER ANY OF THE ABOVE COMMANDS IS CARRIED OUT, A NEW COMMAND
	MAY BE GIVEN.  THE USER MAY SUPPRESS THE PRINTING OF TABLES OR
	ANY OTHER OUTPUT IN ORDER TO GIVE A NEW COMMAND IMMEDIATELY BY
	TYPING <CTRL>O AND PRESSING <RETURN>.  FURTHER EXECUTION OF A
	COMMAND MAY BE HALTED AT ANY BREAK POINT BY TYPING "ABORT".

	WHENEVER THE USER IS EXPECTED TO GIVE A COMMAND OR TO PROVIDE
	CERTAIN INFORMATION NEEDED FOR THE EXECUTION OF A COMMAND, AN
	EXPLANATION OF WHAT IS REQUIRED MAY BE OBTAINED BY TYPING THE
	WORD "EXPLAIN" OR SIMPLY A QUESTION MARK.

	THIS PROGRAM ASSUMES THAT OUTPUT IS TO THE USER TERMINAL.  IF
	OUTPUT TO A FILE ON THE DISK IS DESIRED INSTEAD, THE DISK SHOULD
	BE ASSIGNED LOGICAL UNIT 5 PRIOR TO RUNTIME.

      REMARKS
	THE COMPUTED VALUE OF CHI-SQUARE WITH ONE DEGREE OF FREEDOM
	INCORPORATES A CORRECTION FOR CONTINUITY.  THE CALCULATION OF
	CHI-SQUARE IS ACCOMPANIED BY A WARNING IF THE EXPECTED FREQUENCY
	IS LESS THAN 1 IN ANY CELL OR LESS THAN 5 IN MORE THAN 20 PER
	CENT OF THE CELLS.  KENDALL'S TAU HAS A CORRECTION FOR TIES.

      REFERENCES
	JAMES A. DAVIS, 'ELEMENTARY SURVEY ANALYSIS', PRENTICE-HALL,
	    ENGLEWOOD CLIFFS, N.J., 1971.
	JOHAN GALTUNG, 'THEORY AND METHODS OF SOCIAL RESEARCH', COLUMBIA
	    UNIVERSITY PRESS, NEW YORK, 1967.
	E. TERRENCE JONES, 'CONDUCTING POLITICAL RESEARCH', HARPER &
	    ROW, NEW YORK, 1971.