Table 2. Small sample (simulated) and asymptotic (calculated) relative efficiencies of the estimates of the log-linear interaction parameter. *.

Case-control ratio	Sampling method	Small sample efficiency†	Asymptotic relative efficiency‡
1:1	Matched	0.42	0.40
	Counter-matched	0.43	0.43
	Unmatched	0.30	0.28
	Matched	0.63	0.58
1:2	Counter-matched:
	2 unexposed, 1 exposed	0.89	0.80
	1 unexposed, 2 exposed	0.49	0.45
	Unmatched	0.48	0.44
1:3	Matched	0.74	0.68
	Counter-matched	0.90	0.85
	Unmatched	0.59	0.54
1:5	Matched	0.85	0.78
	Counter-matched	0.95	0.91
	Unmatched	0.73	0.66
1:9	Matched	0.95	0.87
	Counter-matched	0.98	0.95
	Unmatched	0.86	0.78

* Relative efficiencies are given for the model with exp{α} = exp{β} = 2 and exp{γ} = (8/7).

^† The small sample efficiency is the ratio SE²( $\hat{\gamma }$ )_cohort/SE²( $\hat{\gamma }$ )_sample of squared standard errors of the parameter estimates from the simulated data.

^‡ The asymptotic relative efficiency is the ratio SE²( $\hat{\gamma }$ )_cohort/SE²( $\hat{\gamma }$ )_sample of squared asymptotic standard errors.