Table 30.5 Within-class fit report (person class within item).
DIF class specification is: DIF=@GENDER
----------------------------------------------------------------------------------------------------------
| KID OBSERVATIONS BASELINE DIF DIF W-INFIT W-OUTFIT TAP |
| CLASS COUNT AVERAGE EXPECT MEASURE SIZE S.E. MNSQ ZSTD MNSQ ZSTD Number Name |
|--------------------------------------------------------------------------------------------------------|
....
| F 18 .89 .85 -3.38 -.55 .90 .46 -1.22 .19 -.42 9 1-3-2-4 |
| M 16 .88 .92 -3.38 .67 .91 .88 -.02 .23 -.35 9 1-3-2-4 |
| F 18 .72 .65 -1.57 -.58 .68 .80 -.55 .76 .04 10 2-4-3-1 |
| M 16 .69 .77 -1.57 .72 .69 1.47 1.02 .91 .35 10 2-4-3-1 |
Table 30.6 Within-class fit report (item within person class)
DIF class specification is: DIF=@GENDER
----------------------------------------------------------------------------------------------------------
| KID OBSERVATIONS BASELINE DIF DIF W-INFIT W-OUTFIT TAP |
| CLASS COUNT AVERAGE EXPECT MEASURE SIZE S.E. MNSQ ZSTD MNSQ ZSTD Number Name |
|--------------------------------------------------------------------------------------------------------|
....
| F 18 .89 .85 -3.38 -.55 .90 .46 -1.22 .19 -.42 9 1-3-2-4 |
| F 18 .72 .65 -1.57 -.58 .68 .80 -.55 .76 .04 10 2-4-3-1 |
....
| M 16 .88 .92 -3.38 .67 .91 .88 -.02 .23 -.35 9 1-3-2-4 |
| M 16 .69 .77 -1.57 .72 .69 1.47 1.02 .91 .35 10 2-4-3-1 |
For a general description, see Table 30.2
The DIF effects are shown ordered by CLASS within item (column of the data matrix).
KID CLASS identifies the CLASS of persons. KID is specified with PERSON=, e.g., the first CLASS is "F"
OBSERVATIONS are what are seen in the data
COUNT is the number of observations of the classification used for DIF estimation, e.g., 18 F persons responded to TAP item 1.
AVERAGE is the average observation on the classification, e.g., 0.89 is the proportion-correct-value of item 4 for F persons.
COUNT * AVERAGE = total score of person class on the item
BASELINE is the prediction without DIF
EXPECT is the expected value of the average observation when there is no DIF, e.g., 0.92 is the expected proportion-correct-value for F without DIF.
MEASURE is the what the overall measure would be without DIF, e.g., -4.40 is the overall item difficulty of item 4 as reported in Table 14.
DIF SIZE is the size of the DIF
DIF S.E. is the S.E. of the DIF size
W-INFIT is the Within-Group infit statistic for the person CLASS on the item.
W-OUTFIT is the Within-Group outfit statistic for the person CLASS on the item.
MNSQ is the mean-square statistic (chi-square divided by its degrees of freedom).
ZSTD is the mean-square statistic expressed as a z-score (unit normal deviate).
