national multiple family submetering and allocation billing program ...

MATCHED PAIR SAMPLE
The purpose of the site visits/matched pair analysis was to look closely at a small sample
of in-rent and impact 19 properties that have similar characteristics. Properties with similar
characteristics offer a unique opportunity for comparing water use between in-rent and impact
properties, essentially controlling for property differences through the matched pair selection.
Years of experience with survey research have taught water conservation professionals that selfreported
information about water using fixtures like toilets, showerheads, and faucets is often
inaccurate. The site visits were designed to confirm critical information from the manager
survey and fill in additional details as well as information that had gone missing. Most
importantly, the site visits were used to identify first hand the type of water using fixtures found
at the site.
The research plan called for the selection of a matched pair sample from the manager
survey respondents. Although the original plan called only for “pairs” consisting of one impact
to one in-rent, the project’s statistical consultants agreed that if a “triad” could be matched, a
submetered and a RUBS property could be matched with the same in-rent property.
Matched Property Selection
Within each city, pairs or triads were selected to “match” as many critical variables as
possible (based upon the responses of the manager survey). The key variables considered in the
selection process were: year of construction, number of units on the property, average number of
bedrooms per unit, average rent per unit, whether or not their were hook-ups for washing
machines in the units, whether or not the toilets had been replaced, and whether or not the
property was a senior citizen community. The matches were limited to properties classified as
private rentals (mostly apartments), but a few privately owned residences (such as
condominiums) were included out of necessity. In addition, in order to be included in a matched
pair, impacted properties had to have converted to their current billing system by 2001 or earlier.
Any government subsidized housing or mobile home parks were excluded. The researchers were
blind to water use estimates for the properties during the matched property selection process.
Given the relatively small number of impacted properties within each city, it was difficult to
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Impact properties – multi-family properties billing separately for water and/or wastewater services using RUBS,
submetering, hot water hybrid, or other methods.
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