A Guidebook for Using American Community Survey Data for Transportation Planning (2007) / Chapter Skim
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Pages 131-140
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From page 131... ...
• Census data are critical for providing control totals needed in survey expansion efforts. Survey expansion based on variables such as population or households is often performed using 131 C H A P T E R 8 Survey Development and Analysis Using ACS Data 95 U.S.
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From page 132... ...
• Household travel survey conducted by the Central Transportation Planning Staff, Boston, was expanded by vehicles available, household income, and workers in household. • The household survey conducted by the Denver Regional Council of Governments was expanded using household size and income variables at the county level from the census.
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From page 133... ...
Key demographic variables used to weight the household survey data to better reflect the full population of households in the survey area included household size, vehicle ownership, telephone ownership, and county populations. Table 8.1 shows weighting factors based on Census 2000 data.
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From page 134... ...
The actual sampling process employed in the study was a "stratified sample" in which households were randomly selected at the county level. The number of households sampled within a particular county was based on the proportion of households within that county compared to the total number of households in the seven-county 134 A Guidebook for Using American Community Survey Data for Transportation Planning HH Size HH Vehicles 1 Person 2 Persons 3 Persons 4+ Persons 0 Vehicles 0.95000 1.55263 2.72727 2.57143 1 Vehicle 1.00000 0.94720 1.36842 1.57333 2 Vehicles 1.47143 1.01101 0.90146 0.79736 3 Vehicles 0.94118 0.93750 0.85714 1.11570 4+ Vehicles 0.85714 0.75000 0.70588 0.95652 Table 8.1.
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From page 135... ...
Survey Development and Analysis Using ACS Data 135 HH Size HH Vehicles 1 Person 2 Persons 3 Persons 4+ Persons 0 Vehicles 1.2671 1.6872 3.9310 combined 1 Vehicle 0.9357 1.0250 1.4085 2.0036 2 Vehicles 0.9845 0.9263 1.1295 0.9415 3+ Vehicles 0.4383 0.6682 0.8472 0.9429 Table 8.3. Weighting factor to adjust for probability of selection (factor 1)
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From page 136... ...
To determine the weighting factor required in adjusting for episodic telephone ownership, the data were compared to non-telephone ownership as reported by the Census Bureau. In 1990, four percent of households in the seven-county study area were identified as non-telephone households.
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From page 137... ...
Once the year 2000 Long Form census data became available in 2002, the survey data could be reweighted and improved by applying the same weighting process with the updated data. Probability of Selection Table 8.6 shows the new weighting factors for the adjustment related to the probability of selection.
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From page 138... ...
138 A Guidebook for Using American Community Survey Data for Transportation Planning Is Phone Service Episodic? Survey Respondents Survey Proportion Census % Census Adjusted for Episodicity Factor2 No 5,368 0.991 0.9800 0.990 1 Yes 50 0.009 0.0200 0.010 1 Total 5,418 1.000 1.000 1.000 Table 8.7.
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From page 139... ...
We can review the weighting process using ACS estimates and focusing on Franklin County with the objective of understanding how Franklin County weights developed using Census 2000 might differ from those developed using ACS pilot data. Of the 5,418 households surveyed, 3,451 were from Franklin County.
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From page 140... ...
140 A Guidebook for Using American Community Survey Data for Transportation Planning
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