Table 2.

Estimated fixed-effect coefficients of the quadratic and cluster-based models.

Model	Coefficient name	Estimate	SE	DF	t-statistic	p-value	Lower CI (95%)	Upper CI (95%)
Fixed-effect coefficients of the quadratic model	Intercept	0.067	0.026	1077	2.530	0.012	0.015	0.119
	Complexity	-0.045	0.024	1077	-1.912	0.056	-0.092	0.001
	Complexity2	-0.117	0.034	1077	-3.425	<0.001	-0.185	-0.050
Fixed-effect coefficients of the cluster-based model	Intercept	~0	0.048	1076	~0	1	-0.095	0.095
	Complexity	-1.004	0.064	1076	-15.662	<0.001	-1.130	-0.878
	Cluster	~0	0.034	1076	~0	1	-0.067	0.067
	Complexity ∗ Cluster	0.719	0.045	1076	15.978	<0.001	0.631	0.807

The meanings of the abbreviations in the column headers are as follows: SE, standard error; DF, degrees of freedom; CI, confidence interval.