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Table 3 Mean values, item fit statistics and PSI values for three item sets among students in grades 5, 7 and 9. Randomly sampled group sizes of 3500

From: Explaining differential item functioning focusing on the crucial role of external information – an example from the measurement of adolescent mental health

 

Item Set 1 Original 8 items

Item Set 2 Resolving Felt low for boys; girls no period; girls period

Item Set 3 Resolving Felt low and Stomach ache for boys; girls no period; girls period

Difference in difference Set 2 and 3

Difference in difference Set 1 and 2

Difference in difference Set 1 and 3

Boys

1.088

1.065

1.042

   

Girls no period

0.951

0.956

0.985

   

Girls period

0.005

0.056

0.114

   

Difference Boys-Girls no period

0.137

0.109

0.057

0.052

0.028

0.080

Difference Girls no period-Girls period

0.946

0.900

0.871

0.029

0.046

0.075

Person Separation Index

0.76195

0.75846

0.75501

   

Overall item fit Chi Square Probability (adjusted sample size of 1500)

0.005361

0.182495

0.532964

   
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BMC Medical Research Methodology

ISSN: 1471-2288

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