You are here

Omnibus Survey Household Survey Month Specific Information August 2003

Omnibus Survey
Household Survey
Month Specific Information
August 2003

This report provides technical information for the August 2003 Household Survey. Starting in December 2002, the Omnibus Household Surveys are conducted 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 August 2003 survey collected data from August 3, 2003 through August 13, 2003. Data were collected from households in the U.S. using a Random-Digit-Dialed telephone methodology. The final completed sample size is 1,032 cases, and the total number of variables in the public-use dataset is 225. The data were collected by M. Davis and Company (MDAC), under contract with the BTS.

The August 2003 survey collected data from August 8, 2003 through August 22, 2003. Data were collected from households in the U.S. using a Random-Digit-Dialed telephone methodology. The final completed sample size is 1,029 cases, and the total number of variables in the public-use dataset is 240. The data were collected by M. Davis and Company (MDAC), under contract with the BTS.

Sample Telephone Number Selection

There were 6,744 telephone numbers for the August 2003 survey. A total of 4,092 of these numbers were identified as working residential numbers and were divided into 82 replicates. Each of the 66 fielding replicates released initially contained approximately 50 households. Four 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. Four (4) of the 82 August replicates were not utilized in the actual interviewing, resulting in 3,333 numbers being released for use by the telephone interviewers. For this survey, the total number of telephone numbers in the sampling frame, N, is 273,055,800. The total number of telephone numbers in the sample (numbers dialed) was 3,333.

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 sampled households.

Table 1: Number of Telephone Lines per Household

  Value
Mean 1.149
Standard deviation 0.450
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)    32  12,845,409
2 Male - Non-Hispanic Black    47  10,224,033
3 Male - Age 18 – 24 - Non-Hispanic White    23   8,499,919
4 Male - Age 25 – 34 - Non-Hispanic White    43  11,913,170
5 Male - Age 35 – 44 - Non-Hispanic White    70  15,039,201
6 Male - Age 45 – 54 - Non-Hispanic White    79  14,623,075
7 Male - Age 55 – 64 - Non-Hispanic White    54  10,048,666
8 Male - Age 65 or older - Non-Hispanic White    51  11,929,766
9 Male - Non-Hispanic Other    31   5,765,040
10 Female - Hispanic (Any Race)    42  12,298,055
11 Female - Age 18 – 44 - Non-Hispanic Black    26   7,460,884
12 Female - Age 45 or older - Non-Hispanic Black    28   5,469,299
13 Female - Age 18 – 24 - Non-Hispanic White    22   8,568,517
14 Female - Age 25 – 34 - Non-Hispanic White    56  12,118,904
15 Female - Age 35 – 44 - Non-Hispanic White   104  15,364,818
16 Female - Age 45 – 54 - Non-Hispanic White    95  14,962,740
17 Female - Age 55 – 64 - Non-Hispanic White    73  10,641,416
18 Female - Age 65 or older - Non-Hispanic White    85  16,115,329
19 Female - Non-Hispanic Other    24   6,464,326
N/A Missing Demographic Information    47     N/A    
TOTAL 1,032 210,352,567

Data Collection Schedule

The survey was conducted over 11 days to enable 1,000 interviews to be completed. The survey period was from August 3 through August 13.

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 3,692
Telephone Numbers Released 3,333
Telephone Numbers Not Dialed     0
Telephone Numbers Dialed 3,333
Out-of-Scope Numbers (Ineligible)   982
BG - Business   244
CF - Computer/Fax   268
DS - Disconnected number   412
NC - Number change    25
NQ - No one 18 years old or older in household    14
UNB - Unavailable before and during study period    19
Scope Undetermined   423
NA - No answer   328
BZ - Busy     1
AM - Answering machine    32
LM - Left message     3
CCC - Cannot complete call     1
PM - Privacy manager     9
NQL - Eligibility undetermined because of language problems or deafness     7
RFI - Refused to speak with interviewer (screening incomplete)     8
HRI - Hard refusal *     0
OD - Maximum call attempts reached     0
CBU - Callback undetermined    33
CSU - Callback Spanish undetermined     1
In-Scope Numbers 1,928
Complete 1,032
DIP - Reinterview deletion, ineligible person in household interviewed     9
DDA - Reinterview deletion, discrepancy in answers during reinterview     4
CB - Callback   259
CBS - Callback Spanish     0
NAQ - No answer qualified   321
BZQ - Busy qualified     7
AMQ - Answering machine qualified   139
LMQ - Left message qualified     9
CCQ - Cannot complete call qualified     0
PMQ - Privacy manager qualified    10
DL - Deaf/Language    60
RFQ - Respondent refusal    27
UN - Unavailable    29
DR - Respondent deceased prior to completion of interview     0
AC - The area code is changed but not the number     0
HRQ - Hard refusal *    22
CASRO Response Rate 46.73%