Table 2.

Parameter Estimates (SE) of Analysis Results

	Model I. Two-parameter IRT: Baseline items	Model II. Mixed model: Score over time	Model III. Longitudinal IRT: Items over time
Intercepts β0		1.29 (0.02)**
Item
1 β01	−1.49 (0.15)**		−2.12 (0.15)**
2 β02	−0.61 (0.13)**		−0.97 (0.13)**
3 β03	−1.56 (0.16)**		−1.85 (0.16)**
4 β04	−2.69 (0.23)**		−3.00 (0.23)**
5 β05	−4.37 (0.35)**		−5.06 (0.35)**
6 β06	−3.26 (0.26)**		−3.83 (0.26)**
7 β07	−3.41 (0.26)**		−4.22 (0.26)**
8 β08	−4.24 (0.35)**		−5.26 (0.35)**
9 β09	−3.06 (0.28)**		−3.21 (0.28)**
10 β0_10	−5.02 (0.40)**		−4.81 (0.40)**
Slopes β1		0.04 (0.01)**
Item
1 β11			0.02 (0.04)
2 β12			0.09 (0.04)**
3 β13			−0.07 (0.04)
4 β14			−0.04 (0.05)
5 β15			0.31 (0.06)**
6 β16			0.14 (0.05)**
7 β17			−0.04 (0.05)
8 β18			0.17 (0.05)**
9 β19			0.02 (0.05)
10 β1_10			0.18 (0.06)**
Item discriminations
a1	2.65 (0.15)**		1.10 (0.07)**
a2	3.19 (0.16)**		1.24 (0.06)**
a3	2.86 (0.17)**		1.27 (0.07)**
a4	3.29 (0.21)**		1.63 (0.07)**
a5	4.00 (0.28)**		2.44 (0.10)**
a6	3.71 (0.22)**		2.17 (0.08)**
a7	3.11 (0.22)**		1.99 (0.08)**
a8	3.74 (0.28)**		2.82 (0.10)**
a9	4.00 (0.28)**		2.35 (0.09)**
a10	4.67 (0.32)**		2.72 (0.10)**
Random subject effects
συ1 2		0.35 (0.02)**	2.91 (0.08)**
συ1 υ2		−0.009 (0.004)**	−0.14 (0.03)**
συ2 2		0.02 (0.002)**	0.73 (0.03)**
Thresholds
γ2	1.57 (0.04)**		1.73 (0.02)**
γ3	3.74 (0.07)**		4.10 (0.03)**

Note. IRT = item response theory.

*p < .05. **p < .05.