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Omnibus Survey Household Survey Month Specific Information April 2003

Omnibus Survey
Household Survey
Month Specific Information
April 2003

This report presents the results of the April 2003 Omnibus Household Survey. Starting in December 2002, the Omnibus Household Surveys are now fielded on a bi-monthly basis.

Each bi-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 that correspond to one of the U.S. Department of Transportation's (DOT) 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 and will vary from month to month.

The April 2003 survey collected data from April 6, 2003 through April 17, 2003. Data were collected from households in the U.S. using a Random-Digit-Dialed telephone methodology. The final completed sample size is 1,021 cases, and the total number of variables in the public-use dataset is 214. The data were collected by M. Davis and Company (MDAC), under contract with the BTS.

Sample Telephone Number Selection

There were 8,200 telephone numbers for the April 2003 survey. A total of 5,163 of these numbers were identified as working residential numbers and were divided into 103 replicates. Each of the 61 fielding replicates released initially contained approximately 50 households. Two additional replicates were released during Fielding. Eight (8) unused replicates from April's sample were used to conduct a pretest. Each pretest replicate had approximately 50 households. Thirty-four (34) of the 103 April replicates were not utilized in the actual interviewing, resulting in 3,160 numbers being released for use by the telephone interviewers. For this survey, the total number of telephone numbers in the sampling frame, N, is 270,569,400. The total number of telephone numbers in the sample (numbers dialed) is 3,160.

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 1.160
Standard deviation 0.480
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 1.951
Standard deviation 0.862
Minimum     1
25th percentile     1
Median     2
75th percentile     2
Maximum     9

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)    36  10,167,034
2 Male - Non-Hispanic Black    27   9,883,467
3 Male - Age 18 – 24 - Non-Hispanic White    27   8,635,241
4 Male - Age 25 – 34 - Non-Hispanic White    57  11,985,017
5 Male - Age 35 – 44 - Non-Hispanic White    66  15,833,339
6 Male - Age 45 – 54 - Non-Hispanic White    86  14,165,493
7 Male - Age 55 – 64 - Non-Hispanic White    56   9,215,914
8 Male - Age 65 or older - Non-Hispanic White    47  11,755,768
9 Male - Non-Hispanic Other    27   4,146,032
10 Female - Hispanic (Any Race)    45  10,625,145
11 Female - Age 18 – 44 - Non-Hispanic Black    34   7,307,267
12 Female - Age 45 or older - Non-Hispanic Black    25   5,144,462
13 Female - Age 18 – 24 - Non-Hispanic White    13   8,531,226
14 Female - Age 25 – 34 - Non-Hispanic White    50  12,373,489
15 Female - Age 35 – 44 - Non-Hispanic White    88  16,061,583
16 Female - Age 45 – 54 - Non-Hispanic White    88  14,513,973
17 Female - Age 55 – 64 - Non-Hispanic White    48   9,837,412
18 Female - Age 65 or older - Non-Hispanic White   103  15,762,147
19 Female - Non-Hispanic Other    34   4,762,691
N/A Missing Demographic Information    64     N/A    
TOTAL 1,021 200,706,700

Data Collection Schedule

The survey was conducted over 12 days to enable at least 1,000 interviews to be completed. The survey period was from April 6 through April 17.

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 46 percent.

Table 4: Distribution of Household Cases by Disposition

Disposition Category Number of Households
Telephone Numbers Available 4,762
Telephone Numbers Released 3,160
Telephone Numbers Not Dialed     0
Telephone Numbers Dialed 3,160
Out-of-Scope Numbers (Ineligible)   832
BG - Business   191
CF - Computer/Fax   224
DS - Disconnected number   376
NC - Number change    21
NQ - No one 18 years old or older in household     8
UNB - Unavailable before and during study period    12
Scope Undetermined   399
NA - No answer   305
BZ - Busy     0
AM - Answering machine    57
LM - Left message     0
CCC - Cannot complete call     4
PM - Privacy manager    14
NQL - Eligibility undetermined because of language problems or deafness    15
RFI - Refused to speak with interviewer (screening incomplete)     2
HRI - Hard refusal *     0
OD - Maximum call attempts reached     0
CBU - Callback undetermined     2
CSU - Callback Spanish undetermined     0
In-Scope Numbers 1,929
Complete 1,021
DIP - Reinterview deletion, ineligible person in household interviewed     2
DDA - Reinterview deletion, discrepancy in answers during reinterview     5
CB - Callback   220
CBS - Callback Spanish     1
NAQ - No answer qualified   336
BZQ - Busy qualified     0
AMQ - Answering machine qualified   187
LMQ - Left message qualified     3
CCQ - Cannot complete call qualified     3
PMQ - Privacy manager qualified     7
DL - Deaf/Language    53
RFQ - Respondent refusal    12
UN - Unavailable    27
DR - Respondent deceased prior to completion of interview     0
AC - The area code is changed but not the number     0
HRQ - Hard refusal *    52
CASRO Response Rate 46.25%