AN EXAMPLE FOR THE DFITD4 PROGRAM for o scale
30    1.0   .006  1.031  -0.348
111111111111111111111111111111
(32X,2F12.6,12x,f12.6)
(32X,2F12.6,12x,f12.6)
(/35x,F12.6)                




LINE 1: ANY TITLE UP TO 80 CHARACTERS LONG

LINE 2: THE FIRST NUMBER (I3 FORMAT) REPRESENTS THE NUMBER OF ITEMS
        ***
        THE SECOND NUMBER IS SCALAR D (F7.3 FORMAT). D = 1.0 IF
        THE IRT MODEL IS LOGISTIC, AND D= 1.7 IF THE IRT MODEL
        IS NORMAL OGIVE.
        ***
        THE THIRD NUMBER (F7.3 FORMAT)IS THE CUTOFF FOR DTF.
        WE ARE CURRENTLY RECOMMENDING THE FOLLOWING:

                 NUMBER OF OPTIONS       CUTOFF
                         2                .006
                         3                .010
                         4                .013
                         5                .016

        ***
        THE FOURTH AND FIFTH NUMBERS ARE THE MULTIPLICATIVE
        AND ADDITIVE CONSTANTS (F7.3 FORMAT FOR BOTH). THESE
        CONSTANTS ARE USED TO PUT THE REFERENCE GROUP ITEM
        PARAMETERS ON THE SAME SCALE AS THE SCALE UNDERLYING THE
        FOCAL GROUP ITEM  PARAMETERS. IF THE TWO SETS OF ITEM
        PARAMETERS ARE ALREADY ON THE SCALE FOR THE FOCAL GROUP,
        LET THE MULTIPLICATIVE CONSTANT EQUAL 1.0 AND THE ADDITIVE
        CONSTANT EQUAL 0.0.

LINE 3: 1 TELLS THE PROGRAM TO INCLUDE THE ITEM IN THE
        DIF/DTF ANALYSIS; A BLANK WILL EXCLUDE THE ITEM FROM DIF/DTF
        ANALYSIS. FOR EXAMPLE, IF THERE ARE 30 ITEMS IN A TEST AND YOU
        WANT TO EXCLUDE ITEM 3 FROM THE DIF/DTF ANALYSIS, THEN LINE 3
        SHOULD READ AS FOLLOWS:

                               11 111111111111111111111111111

        IF YOU WANT TO INCLUDE ALL 30 ITEMS IN THE ANALYSIS, LINE 3
        SHOULD READ AS FOLLOWS:

                               111111111111111111111111111111  


LINE 4: FORMAT FOR READING THE ITEM PARAMETERS FOR THE FOCAL GROUP,
        a-PARAMETER FOLLOWED BY THE b- AND c-PARAMETERS.

LINE 5: FORMAT FOR READING THE ITEM PARAMETERS FOR THE REFERENCE GROUP,
        a-PARAMETER FOLLOWED BY THE b- AND c-PARAMETERS.

LINE 6: FORMAT FOR READING THE THETA VALUES FOR THE FOCAL GROUP.
        

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            JUST TYPE DFITD4 AND FOLLOW THE INSTRUCTIONS
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