Table 4.

Bland and Altman statistics for sanitary risk observations made by four observers, relative to the ‘gold standard’ Observer A (JOO) (***Indicates significance at alpha = 0.001)

	Versus Observer B	Versus Observer C	Versus Observer D	Versus Observer E	Versus Observer F
No. of water source visits	139	146	53	147	152
Lin’s concordance correlation coefficient (95% confidence intervals)	0.320 (0.22–0.42)	0.515 (0.40–0.63)	0.372 (0.20–0.55)	0.435 (0.33–0.54)	0.230 (0.15–0.31)
Pearson’s r	0.496	0.553	0.504	0.570	0.441
Bias correction factor	0.645	0.931	0.738	0.764	0.521
Average difference in % risk scores (95% limits of agreement)	15.4% (− 14.0% to 44.8%)	5.2% (− 24.4 to 34.8)	12.9% (− 20.5% to 46.4%)	11.9% (− 18.2% to 42.1%)	21.7% (− 15.0% to 58.5%)
Correlation between difference in risk scores and mean	− 0.14	− 0.22	− 0.32	− 0.29	− 0.39
Bradley-Blackwood F test	75.5 (***)	12.9 (***)	19.4 (***)	54.4 (***)	132.8 (***)