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Omnibus Survey Household Survey Results Month Specific Information December 2001

Omnibus Survey
Household Survey Results
Month Specific Information
December 2001

This report presents the results of the December 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 December 2001 survey collected data between December 1, 2001 and December 10, 2001. Data were collected from households in the U.S. using a Random-Digit-Dialed telephone methodology. The final completed sample size is 1,083 cases, and the total number of variables in the public-use dataset is 258. 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 December 2001 survey. A total of 6,931 of these numbers were identified as working residential numbers and were divided into 70 replicates. Each replicate contained approximately 100 households. Four (4) unused replicates from December 2001's sample were used to conduct a pretest. Twenty-five (25) of the 70 December replicates were not utilized in the actual interviewing, resulting in 4,456 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 260,828,700. The total number of telephone numbers in the sample (numbers dialed) is 4,454.

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 1.201
Standard deviation 0.542
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 1.998
Standard deviation 0.851
Minimum     1
25th percentile     1
Median     2
75th percentile     2
Maximum     8

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)    38  10,167,034
2 Male - Non-Hispanic Black    27   9,883,467
3 Male - Age 18 - 24 - Non-Hispanic White    31   8,635,241
4 Male - Age 25 - 34 - Non-Hispanic White    62  11,985,017
5 Male - Age 35 - 44 - Non-Hispanic White    88  15,833,339
6 Male - Age 45 - 54 - Non-Hispanic White    72  14,165,493
7 Male - Age 55 - 64 - Non-Hispanic White    55   9,215,914
8 Male - Age 65 or older - Non-Hispanic White    69  11,755,768
9 Male - Non-Hispanic Other    24   4,146,032
10 Female - Hispanic (Any Race)    44  10,625,145
11 Female - Age 18 - 44 - Non-Hispanic Black    28   7,307,267
12 Female - Age 45 or older - Non-Hispanic Black    16   5,144,462
13 Female - Age 18 - 24 - Non-Hispanic White    35   8,531,226
14 Female - Age 25 - 34 - Non-Hispanic White    73  12,373,489
15 Female - Age 35 - 44 - Non-Hispanic White    96  16,061,583
16 Female - Age 45 - 54 - Non-Hispanic White    75  14,513,973
17 Female - Age 55 - 64 - Non-Hispanic White    76   9,837,412
18 Female - Age 65 or older - Non-Hispanic White   116  15,762,147
19 Female - Non-Hispanic Other    39   4,762,691
N/A Missing Demographic Information    19     N/A    
TOTAL 1,083 200,706,700

Data Collection Schedule

The survey was conducted over a ten-day period, from December 1, 2001 through December 10, 2001. A total of 1,083 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 33.8 percent.

Table 4: Distribution of Household Cases by Disposition

Disposition Category Number of Households
Telephone Numbers Available 6,535
Telephone Numbers Released 4,456
Telephone Numbers Not Dialed     2
Telephone Numbers Dialed 4,454
Out-of-Scope Numbers (Ineligible)   842
BG - Business   224
CF - Computer/Fax   153
DS - Disconnected number   419
NC - Number change    21
NQ - No one 18 years old or older in household     9
UNB - Unavailable before and during study period    16
Scope Undetermined 1,444
NA - No answer   606
BZ - Busy     1
AM - Answering machine   219
LM - Left message     1
CCC - Cannot complete call     0
PM - Privacy manager   124
NQL - Eligibility undetermined because of language problems or deafness    15
RFI - Refused to speak with interviewer (screening incomplete)   133
HRI - Initial Refusal - Requested name be removed from calling list   337
OD - Maximum call attempts reached     8
In-Scope Numbers 2,168
Complete 1,083
Partial Complete    25
CB - Callback   222
CBS - Callback Spanish     5
NAQ - No Answer Qualified   294
BZQ - Busy Qualified     2
AMQ - Answering Machine Qualified   195
LMQ - Left Message Qualified     5
CCQ - Cannot Complete Call Qualified     0
PMQ - Privacy Manager Qualified     72
DL - Deaf/Language    61
RFQ - Respondent refusal    16
UN - Unavailable    75
DR - Respondent deceased prior to completion of interview     0
AC - The area code is changed but not the number     0
HRQ - Qualified Refusal - Requested name be removed from calling list   113
CASRO Response Rate 33.76%