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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.
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