Table 7.

Empirical validity at 6 months using self-reported respiratory health

Measure at 6 months	Categorisation of self-reported respiratory health.	N	Mean	SD	t-statistic	p-value	Relative efficiency
EQ-5D-3 L	Q1 or Q2	90	0.69	0.31	4.14	P < 0.001	1.56
	Q3, Q4 or Q5	33	0.43	0.30
SF-6D	Q1 or Q2	90	0.70	0.13	5.18	P < 0.001
	Q3, Q4 or Q5	32	0.56	0.10

N is the sample size. SD denotes the standard deviation. Relative efficiency statistic is referenced at 1.0 for the EQ-5D-3 L. A relative efficiency value higher than 1.0 shows that the SF-6D is more efficient than the EQ-5D-3 L