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Omnibus Survey Household Survey Results Month Specific Information July 2001

Omnibus Survey
Household Survey Results
Month Specific Information
July 2001

This report presents the results of the July 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 July 2001 survey collected data between July 07 and July 16. Data were collected from households in the U.S. using a Random-Digit-Dialed telephone methodology. The final completed sample size is 1,004 cases, and the total number of variables in the public-use dataset is 204. 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 July 2001 survey. A total of 6.994 of these numbers were identified as working residential numbers and were divided into 70 replicates. Each replicate contained approximately 100 households. Four of the replicates were used to conduct a pretest and 46 replicates were used for the actual interviewing. Twenty four (24) (includes the 4 replicates used for the pretest) of the 70 replicates were not utilized in the actual interviewing. Thus 4,567 numbers were released for use by the telephone interviewers.

For this survey, the total number of telephone numbers in the sampling frame, N, is 257,144,100. The total number of telephone numbers in the sample (numbers dialed) is 4,405.

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 1.22
Standard deviation 0.58
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 1.96
Standard deviation 0.95
Minimum    1
25th percentile    1
Median    2
75th percentile    2
Maximum   15

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)    27  10,167,034
2 Male - Non-Hispanic Black    39   9,883,467
3 Male - Age 18 - 24 - Non-Hispanic White    24   8,635,241
4 Male - Age 25 - 34 - Non-Hispanic White    53  11,985,017
5 Male - Age 35 - 44 - Non-Hispanic White    79  15,833,339
6 Male - Age 45 - 54 - Non-Hispanic White    66  14,165,493
7 Male - Age 55 - 64 - Non-Hispanic White    47   9,215,914
8 Male - Age 65 or older - Non-Hispanic White    63  11,755,768
9 Male - Non-Hispanic Other    32   4,146,032
10 Female - Hispanic (Any Race)    32  10,625,145
11 Female - Age 18 - 44 - Non-Hispanic Black    31   7,307,267
12 Female - Age 45 or older - Non-Hispanic Black    30   5,144,462
13 Female - Age 18 - 24 - Non-Hispanic White    31   8,531,226
14 Female - Age 25 - 34 - Non-Hispanic White    73  12,373,489
15 Female - Age 35 - 44 - Non-Hispanic White    74  16,061,583
16 Female - Age 45 - 54 - Non-Hispanic White    72  14,513,973
17 Female - Age 55 - 64 - Non-Hispanic White    68   9,837,412
18 Female - Age 65 or older - Non-Hispanic White   102  15,762,147
19 Female - Non-Hispanic Other    41   4,762,691
N/A Missing Demographic Information    20     N/A    
TOTAL 1,004 200,706,700

Data Collection Schedule

The survey was conducted over a ten-day period, from July 07 through July 16. A total of 1,004 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 34 percent.

Table 4: Distribution of Household Cases by Disposition

Disposition Category Number of Households
Telephone Numbers Released 4,567
Telephone Numbers Dialed 4,405
Out-of-Scope Numbers (Ineligible)   995
BG - Business   295
CF - Computer/Fax   175
DS - Disconnected Number   449
NC - Number Change    36
NQ - No one 18 years old or older in household    13
UNB - Unavailable before and during study period    27
Scope Undetermined 1,369
NA - No answer   472
BZ - Busy     1
AM - Answering Machine   172
CCC - Cannot complete call    72
PM - Privacy Manager    54
NQL - Eligibility undetermined because of language problems or deafness    23
RFI - Refused to speak with interviewer (screening incomplete)    54
HRI - Requested Name be removed from calling list   359
OD - Maximum call attempts reached   162
In Scope Numbers 2,041
Complete 1,004
Partial Complete    14
CB - Callback   232
CBS - Callback Spanish    56
NAQ - No Answer Qualified   296
BZQ - Busy Qualified     3
AMQ - Answering Machine Qualified   217
LMQ - Left Message Qualified     0
CCQ - Cannot Complete Call Qualified     0
PMQ - Privacy Manager Qualified     4
DL - Deaf/Language    47
RFQ - Respondent Refusal     3
UN - Unavailable    79
DR - Respondent deceased prior to completion of interview     0
AC - The area code is changed but not the number     0
HRQ - Requested name be removed from calling list    86
CASRO Response Rate 33.90%