Case-cohort design in practice – experiences from the MORGAM Project

Table 3 Summary statistics from 5000 replications: sample mean of point estimates, standard deviation of point estimates, sample mean of standard error estimates, power of test for H ₀ : γ = 0 at 5% significance level. Cohort refers to a situation where the covariate in question is collected for every cohort member. SRS refers to subcohort selection with simple random sampling and MORGAM to the subcohort selection procedure described in section 2.3. Weighting method K. & L. refers to Kalbfleisch and Lawless (1988) and ISSP to the inverse subcohort sampling probability weighting as defined in (5).

μ	γ	sampling design	weighting method	mean	sd	mean est. sd	power
0.2	0.0	cohort	-	-0.021	0.256	0.247	0.052
		CC (SRS)	Prentice	-0.001	0.404	0.362	0.076
			K. & L.	-0.001	0.424	0.383	0.075
			ISSP	0.001	0.447	0.402	0.070
		CC (MORGAM)	Prentice	-0.010	0.321	0.310	0.053
			K. & L.	-0.009	0.332	0.325	0.050
			ISSP	-0.009	0.337	0.331	0.049
	0.3	cohort	-	0.296	0.238	0.231	0.283
		CC (SRS)	Prentice	0.325	0.391	0.347	0.188
			K. & L.	0.342	0.411	0.367	0.189
			ISSP	0.355	0.438	0.390	0.174
		CC (MORGAM)	Prentice	0.313	0.312	0.297	0.207
			K. & L.	0.324	0.323	0.312	0.198
			ISSP	0.329	0.330	0.320	0.191
	0.6	cohort	-	0.613	0.226	0.218	0.787
		CC (SRS)	Prentice	0.670	0.393	0.337	0.510
			K. & L.	0.705	0.405	0.354	0.514
			ISSP	0.735	0.449	0.384	0.484
		CC (MORGAM)	Prentice	0.634	0.309	0.287	0.592
			K. & L.	0.660	0.322	0.303	0.582
			ISSP	0.667	0.331	0.313	0.565
0.4	0.0	cohort	-	-0.001	0.204	0.200	0.054
		CC (SRS)	Prentice	0.006	0.333	0.296	0.075
			K. & L.	0.006	0.349	0.313	0.076
			ISSP	0.007	0.368	0.329	0.071
		CC (MORGAM)	Prentice	0.003	0.265	0.251	0.059
			K. & L.	0.003	0.274	0.263	0.058
			ISSP	0.004	0.278	0.268	0.054
	0.3	cohort	-	0.314	0.201	0.196	0.372
		CC (SRS)	Prentice	0.330	0.327	0.294	0.225
			K. & L.	0.347	0.344	0.311	0.223
			ISSP	0.357	0.365	0.328	0.212
		CC (MORGAM)	Prentice	0.317	0.258	0.249	0.253
			K. & L.	0.329	0.266	0.261	0.248
			ISSP	0.332	0.272	0.267	0.238
	0.6	cohort	-	0.629	0.200	0.196	0.890
		CC (SRS)	Prentice	0.663	0.331	0.294	0.606
			K. & L.	0.700	0.347	0.311	0.604
			ISSP	0.721	0.374	0.332	0.586
		CC (MORGAM)	Prentice	0.644	0.261	0.250	0.730
			K. & L.	0.668	0.270	0.262	0.719
			ISSP	0.673	0.277	0.269	0.710