TABLE 7.

Statistical models with logistical regression and binary classification trees^a

Model	Method	Sites	Fraction	Logistic regression				Classification binary trees
				Significant variable(s)	Estimate	P	% Agree- mentb	Tree structure (conditions for V. cholerae positive)	% Agree- mentb
1	Enrichment	B, K, S, H	Water	Intercept	0.2073	0.897	82.2 (90)	If temp is >16.8°C and salinity is <7.5 ppt; if temp is >27.5°C and salinity is between 7.5 and 10.8 ppt	85.6 (90)
Temp	0.1988	0.000
Salinity	−0.5351	0.001
Salinity · salinityc	−0.0791	0.044
2	Enrichment	B, K, S, H	Plankton	Intercept Temp	−1.1753 0.2189	0.343 0.000	87.4 (87)	If temp is >17.8°C and salinity is <9.8 ppt	88.5 (87)
				Salinity	−0.5281	0.000
3	Enrichment	B, K, S, H, cruise	Water	Intercept	−4.1340	0.000	82.3 (130)	If temp is >16.8°C and salinity is <8.9 ppt	82.3 (130)
Temp	0.1713		0.000
				Temp · salinity	−0.0463	0.000
4	Enrichment	B, K, S, H, cruise	Plankton	Intercept	−1.7254	0.133	87.4 (127)	If salinity is <7.5 ppt and temp is >17.5°C	88.2 (127)
Temp	0.1986		0.000
				Salinity	−0.4329	0.000
				Salinity · salinity	0.0184	0.035
5	DFA O1	B, K, S, H	Water	Intercept	−1.1939	0.246	76.9 (108)	If temp is >20.5°C and salinity is <10.3 ppt	81.5 (108)
Temp	0.1233	0.000
				Salinity	−0.1997	0.019
				Temp · salinity	−0.0324	0.005
6	DFA O1	B, K, S, H	Plankton	Intercept	−0.5009	0.668	75.5 (106)	If temp is >12.8°C and salinity is <7.5 ppt; if temp is >12.8°C and salinity is >7.5 ppt and log (calanoid copepods) is >1.56	83.3 (90)
Temp	0.1314	0.001
Salinity	−0.1964	0.034
Temp · salinity	−0.0350	0.020
Temp · temp	−0.0121	0.036

^aThe freshwater site was not included in the analysis. The surface response analysis was performed as described by Carter et al. (7).

^bPercentage of agreement between predicted and observed values. The numbers in parentheses are numbers of samples.

^cA chemical point indicates a cross-product.