Table 1

Hypothetical data for a cohort study of 100000 persons who crashed, classified by seat belt use and death. Percents and arrows show amount and direction of misclassification

Misclassification type	True belt use prevalence	Belted	Died	Lived	Case fatality	Risk ratio
None	6%	Yes	108	5892	0.0180	0.60
		No	2820	91180	0.0300	reference

Differential	6%	Yes	107	6439	0.0166	0.54
			0.6%↓	0.6%↑
		No	2821	90633	0.0302	reference

Differential	35%	Yes	558	41621	0.0132	0.38
			11.5%↓	11.5%↑
		No	2022	55799	0.0350	reference

None	6%	Yes	63	5937	0.0105	0.35
		No	2820	91180	0.0300	reference

Non-differential	6%	Yes	132	8068	0.0161	0.54
			2.5%↕	2.5%↕
		No	2751	89049	0.0300	reference

Non-differential	35%	Yes	408	35343	0.0114	0.38
			2.5%↕	2.5%↕
		No	1910	62339	0.0297	reference