Table 4

Psychometric parameters of items in the original scale

Scales/items	Pearson's correlation	Factor loading	IRT parameters					DIF test for gender
Scales/items	Pearson's correlation	Factor loading	a_i	b₁	b₂	b₃	b_i (mean)	Δa_i	Δb_i
Anxiety
A1. I feel more nervous and anxious than usual.	0.61	0.56	1.40	–0.34	1.58	2.91	1.38	0.09	–0.09
A2. I feel afraid for no reason at all.	0.65	0.62	1.68	0.31	1.68	2.72	1.57	0.41^*	–0.41^*
A3. I get upset easily.	0.72	0.72	2.20	–0.82	0.70	1.89	0.59	0.12	–0.07
A4. I feel that I am going to be crazy.	0.70	0.70	2.28	0.45	1.46	2.21	1.38	0.28	–0.04
A5. I feel weak and get tired easily.	0.70	0.68	1.90	–0.44	0.63	2.10	0.76	0.20	–0.03
A6. I always feel my heart beating fast.	0.63	0.57	1.55	0.23	1.94	2.96	1.71	–0.13	0.39^*
A7. I always feel trouble with breathing.	0.62	0.56	1.66	0.93	2.22	3.18	2.11	–0.03	–0.11
A8. I am bothered by headaches, neck/back pain, or abdominal pain.	0.63	0.56	1.29	–0.27	1.43	2.81	1.32	–0.09	–0.13
A9. I have to empty my bladder often.	0.39	0.28	0.61	–0.38	3.25	6.25	3.04	–0.14	1.00
A10. I fall asleep easily and get a good night's rest.	0.40	0.32	0.56	–1.77	0.61	3.57	0.80	0.03	0.10
A11. I often have nightmares.	0.55	0.59	2.27	0.50	2.11	2.81	1.81	–0.34	0.08
Depression
D1. I feel downhearted and blue.	0.64	0.67	1.89	–0.43	1.40	2.34	1.11	0.18	0.09
D2. I often feel like crying.	0.59	0.59	1.50	–0.21	1.23	2.33	1.12	0.37^*	–0.62^*
D3. I have trouble sleeping at night.	0.52	0.47	1.02	–0.13	1.66	3.00	1.51	0.07	0.15
D4. My heart beats faster than usual.	0.51	0.50	1.26	0.63	2.63	3.67	2.31	–0.08	0.45^*
D5. I eat as much as I used to.	0.37	0.39	1.09	–0.99	0.52	2.16	0.56	0.09	0.12
D6. I get tired for no reason.	0.62	0.64	1.72	–0.32	1.20	2.22	1.03	0.23	–0.05
D7. My mind is as clear as it used to be.	0.50	0.66	1.55	–0.91	0.52	2.01	0.54	0.15	0.05
D8. I am restless and cannot keep still.	0.64	0.69	2.12	–0.33	1.22	2.21	1.03	0.02	0.13
D9. I feel hopeful about the future.	0.46	0.49	1.06	–0.20	1.42	3.23	1.48	0.07	–0.08
D10. I am more irritable than usual.	0.54	0.52	1.26	–0.56	1.37	2.55	1.12	0.07	0.10
D11. I feel I am inferior to my classmates.	0.56	0.48	1.07	–0.71	1.53	2.91	1.24	0.08	–0.24
D12. I am still interested in the things that I used to do.	0.39	0.42	0.99	–0.57	1.16	3.71	1.43	0.14	–0.20
Study problem
ST1. I am not interested in studying.	0.62	0.61	1.89	–0.58	1.37	2.41	1.07	0.46^*	–0.08
ST2. I have to compel myself to study.	0.60	0.57	1.45	–0.88	1.01	2.48	0.87	0.62^*	–0.07
ST3. I am not good at arranging time for study.	0.65	0.64	1.58	–1.25	0.57	2.04	0.45	0.02	–0.08
ST4. I cannot concentrate in class.	0.68	0.69	2.01	–0.89	0.95	2.13	0.73	0.09	0.05
ST5. I never discuss questions with teachers or classmates.	0.51	0.46	0.96	–0.74	1.41	2.90	1.19	–0.11	0.45^*
ST6. I hardly teach myself even if the teacher asks me to.	0.60	0.56	1.42	–0.80	0.92	2.11	0.74	0.06	0.08
ST7. I feel stressful when learning.	0.59	0.59	1.39	–1.50	0.38	1.62	0.17	0.13	0.12
ST8. I feel that I cannot achieve my parents’ or teachers’ expectation.	0.70	0.78	2.98	–0.95	0.25	1.09	0.13	–0.08	0.03
ST9. I become very nervous before examinations.	0.37	0.32	0.79	–0.73	1.71	3.25	1.41	0.25	–0.23
ST10. I have no confidence in accomplishing my schoolwork.	0.69	0.76	2.20	–0.54	0.78	1.60	0.62	0.29	–0.13
ST11. I am always absent from school.	0.27	0.26	1.43	2.77	4.14	4.63	3.85	0.17	0.29^*
ST12. I feel that I cannot adapt myself to the current stage of learning.	0.69	0.69	1.80	–0.32	1.59	2.47	1.25	0.03	–0.17
ST13. I hate studying.	0.69	0.70	2.38	–0.10	1.58	2.26	1.25	0.07	0.01
Sociality problem
SO1. I get along well with my parents.	0.66	0.77	2.87	–0.17	0.93	2.12	0.96	0.27	–0.07
SO2. I would like to talk to my parents when I have troubles.	0.63	0.64	1.61	–1.39	–0.57	0.80	–0.39	0.30	0.18
SO3. I feel that my parents are interfering in my life too much.	0.41	0.37	0.94	–0.60	1.85	2.98	1.41	–0.05	0.47^*
SO4. I feel happy at home.	0.63	0.71	2.16	–0.51	0.54	1.85	0.63	–0.21	–0.06
SO5. I would like to talk to my teachers when I have troubles.	0.50	0.43	0.50	–5.52	–3.66	–0.14	–3.11	–0.15	–0.85
SO6. I get along well with my classmates.	0.59	0.69	3.09	–0.09	1.25	2.48	1.21	0.38	–0.06
SO7. I feel that I can deal with the troubles among classmates well.	0.56	0.60	2.02	–0.50	0.69	2.21	0.80	0.18	–0.05
SO8. I feel that I am often misunderstood by my classmates.	0.36	0.25	0.59	–0.54	3.03	5.25	2.58	0.14	–0.40
SO9. I have friends that I can share my happiness and secrets with.	0.52	0.49	1.19	–0.26	0.96	2.17	0.96	0.13	0.40^*
SO10. I feel happy at school.	0.57	0.58	1.19	–1.12	0.51	2.61	0.67	–0.09	–0.09

a_i: discrimination parameter for item i. b₁ to b₃: difficulty parameters of each category. b_i: mean difficulty parameter for categories 1–4 of item i. Δa_i=a_i (girls)—a_i (boys), Δb_i=b_i (girls)—b_i (boys).
* p<0.001 (the significant level for DIF tests).
DIF, differential item functioning.