TABLE 7.

Analysis of titers reported for round 2 samples A, B, and C tested with the homologous serovar in relation to participation in round 1 of the scheme^a

Parameter	Sample A		Sample B		Sample C
	Ongoing	New	Ongoing	New	Ongoing	New
No. of tests	33	26	29	23	20	12
Mean titer	3.48	3.11	3.10	2.80	2.76	2.43
SD of titer	0.48	0.86	0.61	0.77	0.57	0.90
Coefficient of variation (%)	13.8	27.5	19.7	27.6	20.7	37.0
95% confidence limits of mean	3.31-3.65	2.77-3.45	2.87-3.33	2.48-3.12	2.50-3.02	1.91-2.95

^aTiters are expressed as logarithms to base 10. Overall, for three samples, new participants reported titers that were significantly lower (t_{103 df} = 2.37; P = 0.019) and significantly more variable (F = 12.06; P = 0.001) than those reported by the ongoing participants.