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Omnibus Survey Household Survey Results Month Specific Information August 2001Specific Weight Adjustment for Number of Eligible Household Members

Omnibus Survey
Household Survey Results
Month Specific Information
August 2001

This report presents the results of the August 2001 Household Survey. Each monthly survey will contain a set of core questions that are based on critical information needs within DOT. In addition, supplemental questions will be included each month that correspond to one of DOT's five strategic goals: safety, mobility, economic growth, human and natural environment, and security. Finally, specific questions posed by the various DOT modes will be included in each survey and will vary from month to month.

The August 2001 survey collected data between August 4, 2001 and August 13, 2001. Data were collected from households in the U.S. using a Random-Digit-Dialed telephone methodology. The final completed sample size is 1,038 cases, and the total number of variables in the public-use dataset is 203. The data were collected by M. Davis and Company, under contract with the BTS.

Sample Telephone Number Selection

There were 11,271 telephone numbers purchased for the August 2001 survey. A total of 6,893 of these numbers were identified as working residential numbers and were divided into 69 replicates. Each replicate contained approximately 100 households. Four of the replicates were used to conduct a pretest and 44 replicates were used for the actual interviewing. Twenty-Five (25) (includes the 4 replicates used for the pretest) of the 69 replicates were not utilized in the actual interviewing, resulting in 4,462 numbers being released for use by the telephone interviewers.

For this month’s survey, the total number of telephone numbers in the sampling frame, N, is 257,144,100. The total number of telephone numbers in the sample (numbers dialed) is 4,342.

Specific Weight Adjustment for Households with Multiple Telephone Numbers

Some households have multiple telephone lines for voice communication.

The table below provides summary statistics for the number of telephone lines in the monthly sampled households.

Table 1: Number of Telephone Lines per Household

  Value
Mean 1.203
Standard deviation 0.558
Minimum     1
25th percentile     1
Median     1
75th percentile     1
Maximum     5

Specific Weight Adjustment for Number of Eligible Household Members

The probability of selecting an individual respondent depends upon the number of eligible respondents in the household.The table below provides summary statistics for the number of eligible members in the monthly sampled households.

Table 2: Number of Eligible Household Members

  Value
Mean 2.013
Standard deviation 0.858
Minimum     1
25th percentile     1
Median     2
75th percentile     2
Maximum     6

Post-Stratification Weight Adjustments

Adjusting weighted survey counts so that they agree with population counts provided by the Census Bureau can compensate for different response rates by demographic subgroups, increase the precision of survey estimates, and reduce the bias present in the estimates resulting from the inclusion of only telephone households.

The cells, used to construct post-stratification adjustments for this month, together with the number of sample observations and the national population estimates from the Census Bureau are shown in the table below.

Table 3: Post-Stratification Cells

Cell Description Sample Size Population
1 Male - Hispanic (Any Race)    45 10,167,034
2 Male – Non–Hispanic Black    34  9,883,467
3 Male – Age 18 – 24 – Non–Hispanic White    37  8,635,241
4 Male – Age 25 – 34 – Non–Hispanic White    60 11,985,017
5 Male – Age 35 – 44 – Non–Hispanic White    78 15,833,339
6 Male – Age 45 – 54 – Non–Hispanic White    72 14,165,493
7 Male – Age 55 – 64 – Non–Hispanic White    34  9,215,914
8 Male – Age 65 or older – Non–Hispanic White    70 11,755,768
9 Male – Non–Hispanic Other    32  4,146,032
10 Female – Hispanic (Any Race)    32 10,625,145
11 Female – Age 18 – 44 – Non–Hispanic Black    32  7,307,267
12 Female – Age 45 or older – Non–Hispanic Black    32  5,144,462
13 Female – Age 18 – 24 – Non–Hispanic White    27  8,531,226
14 Female – Age 25 – 34 – Non–Hispanic White    66 12,373,489
15 Female – Age 35 – 44 – Non-Hispanic White    91 16,061,583
16 Female – Age 45 – 54 – Non–Hispanic White    80 14,513,973
17 Female – Age 55 – 64 – Non–Hispanic White    62  9,837,412
18 Female – Age 65 or older – Non–Hispanic White    97 15,762,147
19 Female – Non–Hispanic Other    26  4,762,691
N/A Missing Demographic Information    31    N/A   
TOTAL 1,038 200,706,700

Data Collection Schedule

The survey was conducted over a ten-day period, from August 4, 2001 through August 13, 2001. A total of 1,038 interviews were completed during the survey period.

Disposition of Sample Telephone Numbers

The table below presents the distribution of household telephone numbers by disposition categories. The number of household cases in each category was then used to calculate a CASRO response rate of approximately 35 percent.

Table 4: Distribution of Household Cases by Disposition

Disposition Category Number of Households
Telephone Numbers Available 6,850
Telephone Numbers Released 4,462
Telephone Numbers Not Dialed   120
Telephone Numbers Dialed 4,342
Out-of-Scope Numbers (Ineligible)   953
BG - Business   238
CF - Computer/Fax   229
DS - Disconnected number   428
NC - Number change    40
NQ - No one 18 years old or older in household     6
UNB - Unavailable before and during study period    12
Scope Undetermined 1,357
NA - No answer   462
BZ - Busy     2
AM - Answering machine   155
CCC - Cannot complete call     0
PM - Privacy manager    46
NQL - Eligibility undetermined because of language problems or deafness    19
RFI - Refused to speak with interviewer (screening incomplete)    72
HRI - Initial Refusal - Requested name be removed from calling list   498
OD - Maximum call attempts reached   103
In-Scope Numbers 2,032
Complete 1,038
Partial Complete    17
CB - Callback   221
CBS - Callback Spanish    14
NAQ - No Answer Qualified   222
BZQ - Busy Qualified    15
AMQ - Answering Machine Qualified   176
LMQ - Left Message Qualified     0
CCQ - Cannot Complete Call Qualified     0
PMQ - Privacy Manager Qualified     7
DL - Deaf/Language    57
RFQ - Respondent refusal     8
UN - Unavailable    80
DR - Respondent deceased prior to completion of interview     1
AC - The area code is changed but not the number     0
HRQ - Qualified Refusal - Requested name be removed from calling list   176
CASRO Response Rate 35.12%