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Table 3 Cognitive Domain (3 items) - Overview of final SF-HDQ item level and domain model fit statistics

From: Developing a short-form version of the HIV Disability Questionnaire (SF-HDQ) for use in clinical practice: a Rasch analysis

Item # Final SF-HDQ items Item level statistics
Cognitive domain Location SE Residual ChiSq χ 2 p value
21 Trouble remembering like appointments and when to take medication − 0.072 0.058 2.764* 20.271 0.005*
22 Trouble thinking clearly 0.498 0.061 − 1.078 34.33 < 0.001a
23 Trouble concentrating − 0.427 0.060 − 0.918 21.292 0.003a
Final model: cognitive domain—3 items (raw score range: 0–12)
 Mean − 1.813
 Standard deviation 1.764
 Sample size 730
 Chi-square statistic (df) p value 75.8970 (df: 21); p < 0.001
 Cronbach’s alpha 0.77602
 Person Separation Index 0.70994
 Unidimensionality t-test (% significant) 1.23%
 Differential Item Functioning (DIF) None
  1. *Item fit residual for HDQ21 (2.764) significant (p < 0.017; Bonferroni: 0.05/3) but retained due to clinical importance and need for minimum of 3 items in domain
  2. aSignificant residual (p < 0.017; Bonferroni: 0.05/3) but fit residual F value <  ± 2.5