Table 5 4DSQ items identified with differential item functioning (DIF)
4DSQ scale | Item | Item description | DIFa | Effect sizeb | Directionc |
|---|---|---|---|---|---|
Distress | #25 | Feeling tense | Age | SMD = 0.10/0.14 | 16-44 years > 65+ years |
#26 | Feeling easily irritated | Age | R2 = 3.58; SMD = 0.17/0.25 | 16-44 years > 45+ years | |
#39 | Difficulty getting to sleep | Age | SMD = 0.13 | 16-24 years > 25–44 years | |
|  |  | Education | SMD = 0.11 | lower education > higher education | |
#47 | Fleeting images of past upsetting events | Age | R2 = 2.45; SMD = −0.16/-0.17 | 16-44 years < 65+ years | |
#48 | Put aside thoughts about past upsetting events | Age | SMD = −0.11/-0.14 | 16-44 years < 65+ years | |
Anxiety | #43 | Afraid of public transport | Age | R2 = 3.70 | 25-44 years > 45+ years; 25–44 years > 16–24 years |
#44 | Afraid of embarrassment with other people | Age | R2 = 2.63; SMD = 0.15 | 16-24 years > 45+ years | |
Somatization | #1 | Dizziness/light-headedness | Age | SMD = 0.15/0.18 | 16-24 years > 45+ years |
#2 | Painful muscles | Age | SMD = −0.12/-0.16 | 16-44 years < 65+ years | |
|  |  | Education | SMD = 0.12 | lower education > higher education | |
#6 | Excessive sweating | Age | SMD = 0.11 | 45-64 years > 65+ years | |
#8 | Headache | Age | R2 = 3.93; SMD = 0.17/0.42 | 16-44 years > 45–64 years > 65+ years | |
|  |  | Gender | SMD = 0.13 | Female > male | |
#9 | Bloated feeling in abdomen | Age | SMD = 0.13 | 16-24 years > 65+ years | |
#10 | Blurred vision | Age | SMD = −0.12 | 25-44 years < 65+ years | |
#12 | Nausea or upset stomach | Age | SMD = 0.18/0.22 | 16-24 years > 45+ years | |
#13 | Pain in abdomen or stomach | Age | SMD = 0.18/0.19 | 16-24 years > 45+ years | |
#14 | Tingling in fingers | Age | SMD = −0.11 | 25-44 years > 65+ years | |
#16 | Pain in the chest | Gender | R2 = 3.05 | Female < male |