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Table 3 Summary of DIF by administration mode for each PU-QOL scale

From: Using mixed methods to select optimal mode of administration for a patient-reported outcome instrument for people with pressure ulcers

Scale (no. of items) Uniform   Non-uniform  
(sample size) p < 0.01* p < 0.05* p < 0.01* *p < 0.05*
Pain (11)     
  (n = 70) 0 0 0 1
  (Adjusted n = 200) 1 4 1 1
  (Adjusted n = 300) 4 6 1 4
Exudate (8)     
  (n = 70) 0 0 0 0
  (Adjusted n = 200) 2 3 1 2
  (Adjusted n = 300) 2 4 1 2
Odour (6)     
  (n = 70) 0 1 0 0
  (Adjusted n = 200) 3 3 3 3
  (Adjusted n = 300) 3 4 3 4
Sleep (6)     
  (n = 70) 0 0 0 1
  (Adjusted n = 200) 2 3 3 3
  (Adjusted n = 300) 3 4 3 3
Malaise (3)     
  (n = 70) 0 1 0 0
  (Adjusted n = 200) 2 3 1 1
  (Adjusted n = 300) 2 3 1 2
Mobility (11)     
  (n = 70) 0 1 0 3
  (Adjusted n = 200) 2 3 7 7
  (Adjusted n = 300) 2 4 7 9
Daily activities (9)     
  (n = 70) 0 1 0 1
  (Adjusted n = 200) 2 3 2 5
  (Adjusted n = 300) 3 4 4 6
Mood (7)     
  (n = 70) 0 0 0 1
  (Adjusted n = 200) 0 2 2 4
  (Adjusted n = 300) 0 4 3 5
Anxiety (3)     
  (n = 70) 0 0 0 0
  (Adjusted n = 200) 0 0 0 0
  (Adjusted n = 300) 0 0 0 0
Self-consciousness (7)    
  (n = 70) 0 0 0 0
  (Adjusted n = 200) 1 4 1 2
  (Adjusted n = 300) 3 4 1 3
Autonomy (3)     
  (n = 70) 0 0 0 0
  (Adjusted n = 200) 0 0 2 2
  (Adjusted n = 300) 0 0 2 2
Isolation (4)     
  (n = 70) 0 0 0 1
  (Adjusted n = 200) 1 2 2 3
  (Adjusted n = 300) 2 3 3 3
Participation (9)     
  (n = 70) 0 0 0 2
  (Adjusted n = 200) 4 8 7 7
  (Adjusted n = 300) 6 8 7 7
  1. *Indicates the number of items with DIF at the specified p value.
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