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national multiple family submetering and allocation billing program ...

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made to determine if there are any verifiable water savings associated with RUBS. None of the<br />

models showed a consistent, statistically significant decrease in water use due to RUBS.<br />

Water Use Model #1 – Six Independent Variables<br />

The first multivariate regression model presented uses a limited set of six independent<br />

variables that included average number of bedrooms per unit, year the property was built (1994<br />

<strong>and</strong> earlier or 1995 <strong>and</strong> later), whether the property was a rental property or a non-rental<br />

property, average price charged for water by the local utility, <strong>submetering</strong>, <strong>and</strong> RUBS.<br />

Fundamental information <strong>and</strong> statistics are presented in Table 5.14.<br />

The adjusted coefficient of determination (R 2 ) for the model is 0.224. This value<br />

indicates that this model explains only 22 percent of the variability in the data. The P-value for<br />

the model is 0.00 indicating that whatever fit does exist is statistically significant at the 95%<br />

confidence level.<br />

Table 5.14 Model #1 summary statistics, coefficient of determination, <strong>and</strong> significance<br />

Adjusted R Std. Error of Degrees of<br />

R R Squared<br />

Square the Estimate Freedom F P-value<br />

0. 478 0.229 0.224 21.693 955 46.942 .000<br />

Predictors: (Constant), Submetering, Rental property (compared to individually owned or other), RUBS, Property<br />

built before 1995 (compared to properties built 1995 or later), Utility’s average commodity charge for water <strong>and</strong><br />

wastewater, Average number of bedrooms per unit<br />

Dependent Variable: Indoor water use per unit (average 2001, 2002)<br />

The B coefficients presented in Table 5.15 present the magnitude of the “effect” of the<br />

different independent variables in the model. Of particular interest are the coefficients for RUBS<br />

<strong>and</strong> <strong>submetering</strong>. In Model #1, five factors were statistically significant – average number of<br />

bedrooms per unit, property is a rental (vs. non-rental), year property was built (1994 <strong>and</strong> earlier<br />

or 1995 <strong>and</strong> later), average price charged by the local utility for water <strong>and</strong> wastewater, <strong>and</strong><br />

<strong>submetering</strong>. The only factor that wasn’t statistically significant was RUBS. The effect of<br />

<strong>submetering</strong> <strong>and</strong> RUBS are shown graphically in Figure 5.9 <strong>and</strong> Figure 5.10.<br />

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