Table 3.

Bias and imprecision of population means for the HADS depression subscale, and correlation with quality of life

Method	Bias			Imprecision			Correlation with QoLa
	Random	Demog	Subscale	Random	Demog	Subscale	Random	Demog	Subscale
25 % missing item, rate = psub = 0.5 pitem = 0.5
Subject mean	0.083	0.002	−0.061	0.037	0.033	0.047	−0.754	−0.759	−0.752
Subscale mean	0.004	−0.011	−0.024	0.046	0.051	0.071	−0.722	−0.715	−0.701
Subscale ½ mean	0.000	−0.357	−1.102	0.141	0.258	1.377	−0.756	−0.757	−0.729
Item mean	0.001	−0.360	−1.110	0.062	0.189	1.277	−0.756	−0.721	−0.717
Multiple imputation	0.016	−0.086	−0.324	0.038	0.053	0.175	−0.711	−0.744	−0.729
Multiple imputation ½	0.005	−0.382	−1.218	0.136	0.274	1.638	−0.742	−0.769	−0.732
Complete case	−0.016	−1.026	−3.168	0.348	1.347	10.162	−0.769	−0.769	−0.427
10 % missing item rate, psub = 0.5 pitem = 0.2
Subject mean	0.028	0.002	−0.025	0.010	0.009	0.013	−0.768	−0.769	−0.768
Subscale mean	−0.003	0.001	−0.002	0.010	0.010	0.015	−0.760	−0.768	−0.754
Subscale ½ mean	−0.000	−0.025	−0.067	0.016	0.019	0.026	−0.769	−0.768	−0.743
Item mean	−0.002	−0.123	−0.372	0.014	0.030	0.154	−0.758	−0.755	−0.743
Multiple imputation	0.005	−0.012	−0.075	0.011	0.012	0.023	−0.766	−0.765	−0.765
Multiple imputation ½	0.003	−0.033	−0.130	0.016	0.021	0.040	−0.770	−0.769	−0.746
Complete case	−0.000	−0.695	−2.122	0.201	0.699	4.720	−0.770	−0.770	−0.716
10 % missing item rate, psub = 0.2 pitem = 0.5
Subject mean	0.034	0.003	−0.082	0.014	0.014	0.025	−0.764	−0.767	−0.765
Subscale mean	0.000	−0.006	−0.010	0.018	0.020	0.028	−0.750	−0.747	−0.740
Subscale ½ mean	0.002	−0.134	−0.701	0.041	0.064	0.575	−0.764	−0.766	−0.730
Item mean	−0.002	−0.132	−0.702	0.022	0.041	0.514	−0.745	−0.746	−0.731
Multiple imputation	−0.005	−0.027	−0.234	0.013	0.015	0.080	−0.761	−0.761	−0.758
Multiple imputation ½	−0.000	−0.139	−0.774	0.040	0.064	0.672	−0.766	−0.769	−0.734
Complete case	−0.003	−0.285	−1.540	0.077	0.161	2.409	−0.768	−0.772	−0.666
2 % missing item rate, psub = 0.1 pitem = 0.2
Subject mean	0.006	−0.000	−0.023	0.002	0.002	0.003	−0.769	−0.771	−0.771
Subscale mean	−0.000	−0.000	0.001	0.002	0.002	0.003	−0.767	−0.767	−0.767
Subscale ½ mean	0.000	−0.009	−0.034	0.003	0.004	0.010	−0.768	−0.768	−0.766
Item mean	0.000	−0.029	−0.166	0.003	0.004	0.033	−0.766	−0.766	−0.767
Multiple imputation	0.001	−0.004	−0.038	0.002	0.002	0.005	−0.768	−0.769	−0.769
Multiple imputation ½	0.001	−0.01	−0.068	0.003	0.004	0.014	−0.769	−0.769	−0.768
Complete case	−0.000	−0.119	−0.679	0.026	0.043	0.500	−0.770	−0.770	−0.729

N = 52 for random, demographic dependent and subscale dependent missingness mechanisms. 1000 simulated datasets

^aCorrelation = −0.767 for original data (n = 1444)