﻿ Table 31.4 Differential person functioning DPF fit summary

# Table 31.4 Differential person functioning DPF fit summary

Table 31.4 summarizes the CLASS Differential Person Functioning statistics for each person shown in Table 31.2. Table 31.2 shows a t-statistic for each CLASS. These are summarized as chi-square statistics for each person, indicating whether the observed DPF within each person is due to chance alone. The null hypothesis is that the DPF is statistically zero across the classes. Please do not use anchoring  (IAFILE=, PAFILE=, SAFILE=) when investigating this Table.

DPF class/group specification is: DPF=\$S1W1

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| TAP        SUMMARY DPF               BETWEEN-CLASS       KID               |

| CLASSES    CHI-SQUARE   D.F.  PROB.  MEAN-SQUARE t=ZSTD  Number Name       |

|----------------------------------------------------------------------------|

|       2         .2914      1  .5893       .2291  -.3520       1 Adam    M  |

TAP CLASSES/GROUPS is the count of item CLASSES or GROUPS for the person.

SUMMARY DIF CHI-SQUARE is the sum of the squared normalized t-statistic values from Table 31.2.

D.F. is the degrees of freedom, the count of CLASSES or GROUPS contributing to the chi-square less 1.

PROB. is the probability of the chi-square. Values less than .05 indicate statistical significance.

BETWEEN-CLASS/GROUP are Between-Group Fit Statistics, testing the hypothesis: "The dispersion of the group measures accords with Rasch model expectations."

MEAN-SQUARE is chi-square divided by its degrees of freedom. It is the size of the misfit (expectation = 1.0, overfit <1.0, underfit >1.0).

t=ZSTD is the significance of the MEAN-SQUARE standardized as a unit-normal deviate (t-statistic with infinite degrees of freedom).

KID is the person. Number is the person entry number. Name is the person label.

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