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Omnibus Survey Household Survey Month Specific Information August 2002

Omnibus Survey
Household Survey
Month Specific Information
August 2002

This report presents the results of the August 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 August 2002 survey collected data from August 03, 2002 through August 12, 2002. Data were collected from households in the U.S. using a Random-Digit-Dialed telephone methodology. The final completed sample size is 1,106 cases, and the total number of variables in the public-use dataset is 174. 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 August 2002 survey. A total of 5,139 of these numbers were identified as working residential numbers and were divided into 102 replicates. Each of the 66 fielding replicates released initially contained approximately 50 households. No additional replicates were released during Fielding. Eight (8) unused replicates from August’s sample were used to conduct a pretest. Each pretest replicate had approximately 50 households. Twenty-eight (28) of the 102 August replicates were not utilized in the actual interviewing, resulting in 3,339 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 3,339.

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 0.455
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 2.013
Standard deviation 0.933
Minimum     1
25th percentile     1
Median     2
75th percentile     2
Maximum    11

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)    41  10,167,034
2 Male - Non-Hispanic Black    42   9,883,467
3 Male - Age 18 – 24 - Non-Hispanic White    31   8,635,241
4 Male - Age 25 – 34 - Non-Hispanic White    52  11,985,017
5 Male - Age 35 – 44 - Non-Hispanic White    91  15,833,339
6 Male - Age 45 – 54 - Non-Hispanic White    94  14,165,493
7 Male - Age 55 – 64 - Non-Hispanic White    52   9,215,914
8 Male - Age 65 or older - Non-Hispanic White    56  11,755,768
9 Male - Non-Hispanic Other    30   4,146,032
10 Female - Hispanic (Any Race)    48  10,625,145
11 Female - Age 18 – 44 - Non-Hispanic Black    37   7,307,267
12 Female - Age 45 or older - Non-Hispanic Black    19   5,144,462
13 Female - Age 18 – 24 - Non-Hispanic White    25   8,531,226
14 Female - Age 25 – 34 - Non-Hispanic White    66  12,373,489
15 Female - Age 35 – 44 - Non-Hispanic White    95  16,061,583
16 Female - Age 45 – 54 - Non-Hispanic White   106  14,513,973
17 Female - Age 55 – 64 - Non-Hispanic White    62   9,837,412
18 Female - Age 65 or older - Non-Hispanic White   103  15,762,147
19 Female - Non-Hispanic Other    33   4,762,691
N/A Missing Demographic Information    23     N/A    
TOTAL 1,106 200,706,700

Data Collection Schedule

The survey was conducted over a ten-day period, from August 03 through August 12. A total of 1,106 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 48 percent.

Table 4: Distribution of Household Cases by Disposition

Disposition Category Number of Households
Telephone Numbers Available 4,739
Telephone Numbers Released 3,339
Telephone Numbers Not Dialed     0
Telephone Numbers Dialed 3,339
Out-of-Scope Numbers (Ineligible)   889
BG - Business   189
CF - Computer/Fax   304
DS - Disconnected number   358
NC - Number change    20
NQ - No one 18 years old or older in household     8
UNB - Unavailable before and during study period    10
Scope Undetermined   445
NA - No answer   308
BZ - Busy     0
AM - Answering machine    46
LM - Left message    32
CCC - Cannot complete call     1
PM - Privacy manager    13
NQL - Eligibility undetermined because of language problems or deafness    28
RFI - Refused to speak with interviewer (screening incomplete)    0
HRI - Hard refusal    10
OD - Maximum call attempts reached     7
CBU - Callback Undetermined     0
CSU - Callback Spanish Undetermined     0
In-Scope Numbers 2,005
Complete 1,106
Partial Complete    22
CB - Callback   155
CBS - Callback Spanish     1
NAQ - No Answer Qualified   296
BZQ - Busy Qualified     0
AMQ - Answering Machine Qualified   146
LMQ - Left Message Qualified    17
CCQ - Cannot Complete Call Qualified     0
PMQ - Privacy Manager Qualified     3
DL - Deaf/Language    51
RFQ - Respondent refusal    24
UN - Unavailable    60
DR - Respondent deceased prior to completion of interview     0
AC - The area code is changed but not the number     0
HRQ - Hard refusal   124
CASRO Response Rate 47.81%