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Table 3 Analyses of differential item functioning (DIF)

From: Cross-cultural validation of the German and Turkish versions of the PHQ-9: an IRT approach

  DIF related to languagea DIF related to ethnicity and migration backgroundb
Item Totalc Slope parameterd Location parameterse Totalc Slope parameterd Location parameterse
1. Anhedonia 10.9* 6.4* 4.5 2.2 0.4 1.8
2. Depressed mood 4.3 0.5 3.8 4.0 0.3 3.7
3. Sleep problems 8.3 0.1 8.3* 5.3 0.4 4.9
4. Low energy 11.2* 0.0 11.2* 2.8 0.1 2.7
5. Appetite changes 19.7*** 3.3 16.4*** 14.8** 0.3 14.5**
6. Low self-esteem 3.6 0.3 3.3 0.2 0.0 0.2
7. Concentration difficulties 5.1 0.2 4.8 18.7*** 6.8** 12.0**
8. Psychomotor changes 4.2 0.0 4.2 1.9 0.1 1.9
9. Suicidal ideation 5.6 0.4 4.2 3.0 0.3 2.7
  1. We report X2 statistics. Significant X2 tests indicate that there is a difference in item functioning. Results for anchor items are printed in italics. X2 values for anchor items are reported from the last iteration of step one, where anchor items have been selected and purified. Candidate for DIF items are in bold, and X2 values are those estimated from the second stage of analysis, i.e. where candidate DIF items were tested against the previously identified set of DIF-free anchor items
  2. aAnalysis 1 comparing T-G (Turkish immigrants completing the German version of the PHQ-9, n = 191) with T-T (Turkish immigrants completing the Turkish version of the PHQ-9, n = 116). bAnalysis 2 comparing G-G (Germans with no migration background completing the German version of the PHQ-9, n = 1670) with T-G (Turkish immigrants completing the German version of the PHQ-9, n = 191). cdf = 4. ddf = 1. edf = 3
  3. *p < .05, **p < .01, ***p < .001