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Omnibus Survey Household Survey Results Month Specific Information April 2002

Omnibus Survey
Household Survey Results
Month Specific Information
April 2002

This report presents the results of the April 2002 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 April 2002 survey collected data between April 6, 2002 and April 15, 2002. Data were collected from households in the U.S. using a Random-Digit-Dialed telephone methodology. The final completed sample size is 1,014 cases, and the total number of variables in the public-use dataset is 193. The data were collected by M. Davis and Company, under contract with the BTS.

Sample Telephone Number Selection

There were 8,200 telephone numbers purchased for the April 2002 survey. A total of 5,011 of these numbers were identified as working residential numbers and were divided into 50 replicates. Each replicate contained approximately 100 households. Four (4) unused replicates from April's sample were used to conduct a pretest. Eleven (11) of the 50 April replicates were not utilized in the actual interviewing, resulting in 3,511 numbers being released for use by the telephone interviewers. For this survey, the total number of telephone numbers in the sampling frame, N, is 261,905,600. The total number of telephone numbers in the sample (numbers dialed) is 3,511.

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 1.175
Standard deviation 0.501
Minimum     1
25th percentile     1
Median     1
75th percentile     1
Maximum     4

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 1.977
Standard deviation 0.845
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)    35  10,167,034
2 Male - Non-Hispanic Black    27   9,883,467
3 Male - Age 18 - 24 - Non-Hispanic White    30   8,635,241
4 Male - Age 25 - 34 - Non-Hispanic White    55  11,985,017
5 Male - Age 35 - 44 - Non-Hispanic White    73  15,833,339
6 Male - Age 45 - 54 - Non-Hispanic White    74  14,165,493
7 Male - Age 55 - 64 - Non-Hispanic White    57   9,215,914
8 Male - Age 65 or older - Non-Hispanic White    51  11,755,768
9 Male - Non-Hispanic Other    42   4,146,032
10 Female - Hispanic (Any Race)    38  10,625,145
11 Female - Age 18 - 44 - Non-Hispanic Black    32   7,307,267
12 Female - Age 45 or older - Non-Hispanic Black    20   5,144,462
13 Female - Age 18 - 24 - Non-Hispanic White    27   8,531,226
14 Female - Age 25 - 34 - Non-Hispanic White    69  12,373,489
15 Female - Age 35 - 44 - Non-Hispanic White    84  16,061,583
16 Female - Age 45 - 54 - Non-Hispanic White    85  14,513,973
17 Female - Age 55 - 64 - Non-Hispanic White    75   9,837,412
18 Female - Age 65 or older - Non-Hispanic White    89  15,762,147
19 Female - Non-Hispanic Other    32   4,762,691
N/A Missing Demographic Information    19     N/A    
TOTAL 1,014 200,706,700

Data Collection Schedule

The survey was conducted over a ten-day period, from April 6, 2002 through April 15, 2002. A total of 1,014 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 40 percent.

Table 4: Distribution of Household Cases by Disposition

Disposition Category Number of Households
Telephone Numbers Available 4,611
Telephone Numbers Released 3,511
Telephone Numbers Not Dialed     0
Telephone Numbers Dialed 3,511
Out-of-Scope Numbers (Ineligible)   733
BG - Business   191
CF - Computer/Fax   153
DS - Disconnected number   336
NC - Number change    27
NQ - No one 18 years old or older in household    15
UNB - Unavailable before and during study period    11
Scope Undetermined  818
NA - No answer   361
BZ - Busy     0
AM - Answering machine   143
LM - Left message    14
CCC - Cannot complete call     2
PM - Privacy manager    42
NQL - Eligibility undetermined because of language problems or deafness    31
RFI - Refused to speak with interviewer (screening incomplete)    55
HRI - Hard refusal   170
OD - Maximum call attempts reached     0
In-Scope Numbers 1,960
Complete 1,014
Partial Complete    10
CB - Callback   265
CBS - Callback Spanish     9
NAQ - No Answer Qualified   297
BZQ - Busy Qualified     1
AMQ - Answering Machine Qualified   188
LMQ - Left Message Qualified    16
CCQ - Cannot Complete Call Qualified     3
PMQ - Privacy Manager Qualified    10
DL - Deaf/Language    59
RFQ - Respondent refusal     4
UN - Unavailable    46
DR - Respondent deceased prior to completion of interview     0
AC - The area code is changed but not the number     0
HRQ - Hard refusal    38
CASRO Response Rate 39.68%