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Table 5.29 Paired samples test, submetered converted properties<br />

Paired Differences<br />

Estimated Annual Water Use per Unit<br />

Prior to Conversion - Estimated Annual<br />

Water Use per Unit After Conversion<br />

Mean<br />

Difference<br />

Std.<br />

Deviation<br />

Std.<br />

Error<br />

Mean t df<br />

P-<br />

value<br />

17.500 17.675 7.216 2.425 5 0.060<br />

40<br />

Difference in Annual Water Use<br />

per Unit Pre <strong>and</strong> Post Conversion (kgal)<br />

30<br />

20<br />

10<br />

0<br />

-10<br />

-20<br />

-30<br />

-4.35<br />

-17.50<br />

-2.48<br />

-40<br />

All Properties<br />

N=46<br />

Submetered<br />

N=6<br />

RUBS<br />

N=39<br />

Figure 5.19 Difference in average annual water use, pre- <strong>and</strong> post-conversion<br />

Differences among properties who converted to RUBS were also looked at separately.<br />

This sample size was larger (39 properties), which is not surprising since retrofitting a property<br />

with a RUBS system requires very few up front costs <strong>and</strong> does not require any plumbing<br />

modifications. Among these properties, savings averaged 2.5 kgal per unit per year, but were not<br />

found to be statistically significant (see Table 5.30 <strong>and</strong> Table 5.31).<br />

175

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