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Table 3.8 Comparison of annual water use per unit in manager survey respondent<br />

properties <strong>and</strong> postcard survey respondent properties<br />

Billing Method<br />

Survey<br />

Postcard Manager<br />

In-rent or HOA<br />

Avg 2001 Water Use per Unit (kgal)* 53.95 † 51.56 †<br />

Number N=6437 N=847<br />

Submetered<br />

Avg 2001 Water Use per Unit (kgal)* 44.76 46.20<br />

Number N=259 N=113<br />

RUBS<br />

Avg 2001 Water Use per Unit (kgal)* 52.97 54.85<br />

Number N=582 N=175<br />

Hot water Avg 2001 Water Use per Unit (kgal)* 51.85 47.17<br />

hybrid Number N=41 N=22<br />

All Designated Estimated 2001 Water Use 53.54 † 51.45 †<br />

Properties ‡ Number N=7319 N=1157<br />

* Includes properties that were missing 2 or less months of data, where the average 2001 water use per unit is<br />

greater than 6 <strong>and</strong> less than 200 kgal/unit. Impact manager survey properties only include properties that converted<br />

to separate <strong>billing</strong> in 2000 or earlier.<br />

†<br />

Significant differences measured between the two groups using a t-test at the 0.05 level.<br />

‡<br />

Includes all properties that are in-rent, submetered, RUBS, or hot water hybrid, but excludes any properties that<br />

indicated “other” or left the question blank. In addition, any property that left the number of units blank was<br />

excluded.<br />

DATA ANALYSIS<br />

Database Development<br />

Development of the database for the Study was an on-going process beginning with the<br />

historic <strong>billing</strong> data obtained from each of the 13 study sites. Microsoft Access is a relational<br />

database that organizes data into a series of tables that can be linked with a common field. For<br />

this study a separate database was developed for each of the participating utilities. Each utility’s<br />

database contained the same set of tables:<br />

• Historic <strong>billing</strong> data on the sample frame accounts<br />

• Survey data – coded responses from the mailed surveys<br />

Each of these tables contained a common field called “PROPID” which was a unique<br />

number assigned during survey coding. The PROPID field enabled linking of survey data with<br />

historic <strong>billing</strong> data <strong>and</strong> allowed database <strong>program</strong>mers to develop any number of queries on the<br />

database to retrieve a wide variety of information. The PROPID also protected the privacy of<br />

individual respondents.<br />

53

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