Table 5 Differential item functioning positive and negative symptoms: reference group = USA vs. focal group = India and East & Maritime Asia

Item

p-value

E.S. (95% C.I.)

Class

India

p-value

E.S. (95% C.I.)

Class

Eastern Asia

USA Mean

P1

0.12

−0.15 (−0.32;0.02)

A

4.19 (0.99)

0.01

−0.32 (−0.52;-0.13)

BB-

3.89 (1.01)

4.29 (1.05)

P2

0.94

0.06 (−0.17;0.29)

A

3.46 (1.32)

0.19

0.29 (0.06;0.52)

AA

3.52 (1.81)

3.42 (1.34)

P3

< 0.001

0.25 (0.10;0.40)

A

4.53 (0.96)*

0.94

−0.03 (−0.23;0.17)

AA

4.06 (1.18)

4.33 (0.96)

P4

0.53

−0.07 (−0.22;0.07)

A

2.55 (1.18)

0.01

0.19 ( 0.03;0.36)

AA

2.43 (1.12)

2.70 (1.80)

P5

0.11

−0.16 (−0.34;0.02)

A

3.08 (1.70)

0.01

−0.28 (−0.49;-0.06)

AA

2.47 (1.65)

3.34 (1.33)

P6

< 0.001

−0.37 (−0.53;-0.21)

B-

4.25 (0.78)*

0.02

−0.29 (−0.46;-0.11)

AA

4.16 (0.87)

4.64 (1.02)

P7

< 0.001

0.44 (0.26;0.61)

B+

3.39 (0.86)*

< 0.001

0.43 (0.23;0.64)

BB+

3.07 (1.06)*

3.05 (1.26)

N1

0.01

−0.20 (−0.34;-0.06)

AA

4.05 (1.50)

0.76

0.09 (−0.06;0.24)

AA

3.85 (1.66)

4.01 (1.67)

N2

0.9

0.01 (−0.09;0.12)

AA

3.85 (0.77)

0.44

−0.10 (−0.21;0.01)

AA

3.65 (0.69)

3.85 (0.79)

N3

< 0.001

0.31 (0.17;0.45)

BB+

3.66 (1.41)*

0.06

0.16 (0.01;0.30)

AA

3.00 (1.29)

3.26 (1.51)

N4

< 0.001

−0.23 (−0.37;-0.09)

AA

3.55 (1.01)*

0.03

−0.16 (−0.29;-0.04)

AA

3.34 (0.77)

3.74 (1.23)

N5

0.16

−0.15 (−0.33;0.03)

AA

4.14 (1.23)

0.21

−0.12 (−0.31;0.06)

AA

3.83 (1.41)

4.16 (1.32)

N6

< 0.001

0.29 (0.13;0.44)

AA

4.06 (1.62)*

0.98

−0.01 (−0.16;0.14)

AA

3.24 (1.33)

3.52 (1.73)

N7

0.88

−0.03 (−0.22;0.17)

AA

2.89 (1.21)

0.09

0.15 (−0.02;0.33)

AA

2.88 (1.83)

2.17 (1.15)