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Table 4 Difficulty of repeated non-anchor items

From: Implementing statistical equating for MRCP(UK) parts 1 and 2

  Occasion Mean difficulty SD difficulty Occasion Mean difficulty SD difficulty N Correlation Difficulty difference t df p
Part 1 First -.035 .891 Second -.045 .941 477 .742 .001 .318 476 .751
Part 1 First -.210 .859 Third -.157 .826 55 .755 -.053 -.664 54 .510
Part 1 Second .000 .905 Third .143 .651 12 .714 -.143 -.779 11 .452
Part 2 First -.065 .891 Second -.123 1.001 279 .604 .058 1.076 278 .283
  1. Difficulties (1-IRT) of non-anchor items used on two occasions (first and second, first and third, or second and third usage), shown as mean and SD on each occasion, with mean difficulty, and paired t-test for difference in difficulties across occasions.