OHS OMB package-Section B 8-15-07

RESEARCH AND INNOVATIVE TECHNOLOGY ADMINISTRATION

Bureau of Transportation Statistics

OMB Clearance Package

Section B

for

Clearance to conduct the OMNIBUS HOUSEHOLD SURVEY

from FY 2007 through FY 2009

Prepared by

Office of Advanced Studies

Bureau of Transportation Statistics

Research and Innovative Technology Administration

August 15, 2007

Table of Contents

B. Collection of Information employing statistical methods

1. Description of Activity

2. Procedures for the Collection of Information

3. Non-response, Maximization of Response Rates, Accuracy and Reliability

4. Test of Procedures

5. Personnel/Organizations Responsible for Design, Collection, or Analysis of the Information

B. Collection of Information Employing Statistical Methods

1. Respondent Universe and Sampling Methods

The potential respondent universe or population for the RITA/BTS Omnibus Household Survey is the non-institutionalized population, aged 18 and older, who live in the United States. The sampling frame for the Omnibus Household Survey will be a list-assisted random digit dialing (RDD) sample of U.S. residential telephone numbers. The survey contractor uses a sampling frame constructed to produce samples that are proportional to population density, resulting in nationally representative samples of residential telephone numbers. Individual survey respondents within selected households will be chosen at random. Based on similar surveys, a sample will consist of 3000-5,000 usable phone numbers.

The contractor will select a “nation-wide” sample that: 1) is a probability sample which conforms to list-assisted random digit dialing (RDD) methodology, 2) is representative of the 50 United States and the District of Columbia, 3) uses a random method to select the adult household respondent. The contractor will ensure that the sample includes only individuals who are 18 years of age or older (adults) and are non-institutionalized. There will be a minimum of at least 1,000 completed interviews for the “nation-wide” sample with a minimum response rate of 50 percent. In addition, the contractor will select a “targeted” sample of households in large metropolitan areas using the same sampling methodology specified for the “nation-wide” sample. There will be a minimum of at least 500 completed interviews for the “targeted” sample with a minimum response of 50 percent.

Attachment 1 is the November 2006 codebook for the OHS. This attachment contains details on the nation-wide sample design, weighting procedures, response rate calculations, data collection schedule, interviewing procedures, and quality control procedures for the survey.

2. Procedures for the Collection of Information

Data will be collected from individuals within sampled households. Based on projected contact rates, refusal rates, and response rates, sample size for the Omnibus Household Survey will be selected to yield approximately 1,500 completed interviews per data collection effort. This sample size will be adequate for making inferences to the population on selected variables using one way and simple multi-way analyses. Other variables and more complex multi-way analyses will require multiple data collection periods to achieve the accuracy needed for making population inferences.

The OHS schedule is extremely tight to accommodate the needs of the different departmental administrations for fast turnaround of performance and customer satisfaction information. In general, data collection will begin on the first week of the month. The data collection period will last up to one month or 31 calendar days. Professional survey interviewers will interview respondents by telephone and enter responses into computer-assisted telephone interviewing (CATI) questionnaires. Immediately following data collection, data will be processed into a public use micro data file and delivered to RITA/BTS.

The data processing step includes computing and assigning weights to adjust data to population totals, account for unequal probabilities of sample selection, and non-response. Public use data will be stripped of all identifying information (such as names and telephone numbers) and disclosure limitation methods will be applied.

3. Methods to Maximize Response Rates and Deal with Issues of Non-response

The OHS response rates have dramatically improved since the survey began in August 2000 due to implementation of specific response rate improvement techniques. These techniques include the use of an advance letter to inform households about the survey and to let them know that an interviewer will call; repeated callback attempts for each telephone number; availability of a toll-free number for respondents to call in to complete the interview in the event they are not home when the interviewer calls and leaves a message; and the use of refusal avoidance specialists at the telephone call centers to convince a reluctant respondent to participate. We expect to continue the use of these techniques for future Omnibus Household Surveys.

Despite our best efforts, however, some non-response will occur, because the survey is voluntary and respondents do have the right of refusal. The OHS has consistently resulted in response rates around 50 percent. While this is not unreasonable for a customer satisfaction RDD survey, it is not satisfactory for us in terms of potential non-response bias. RITA/BTS has plans to conduct a thorough study of non-response bias for the OHS. Components of the study will include the following:

1) RITA/BTS will compare values of key variables aggregated within the “early respondent” and “late respondent” categories. The survey’s late respondents (those who proved difficult to contact or who were initially reluctant to respond) will serve as proxies for the non-respondents. Any large differences between these two groups will be interpreted as evidence of non-response bias.

2) Based on detailed comparisons between the early respondent and late respondent groups (disaggregated into smaller categories defined by time of response), RITA/BTS will investigate the possibility of using statistical models to estimate the extent of non-response bias for key variables.

3) In addition, RITA/BTS will attempt to map telephone exchanges from our RDD survey to census tracts or zip codes, and then match aggregated data from the Census long form to compare respondents and non-respondents at an area level (as opposed to the specific household).

4) RITA/BTS will continue the general investigation it is currently conducting on non-response bias in RDD household surveys on transportation-related topics. Adjustments for non-response will be made during the development of the final weights in order to improve data reliability and generalize results to the population of inference.

4. Test of Procedures

The OHS was reviewed in June of 2005 by an outside panel of experts in transportation and/or survey methodology. The OHS was cognitively tested in July 2005 at the Bureau of Labor Statistics Behavioral Science Research Laboratory. The OHS contractors pre-test the questionnaire prior to interviewing. RITA/BTS staff also pretest the questionnaire during development, as well as when the programmed version of the questionnaire is delivered from the Contractor. In addition, staff members with an expertise in survey research methods are utilized prior to and after pretesting to conduct an “expert review” of the survey questions and the overall questionnaire flow and format.

5. General Customer Satisfaction Surveys Program Procedures for Submitting packages to OMB.

This is not a customer satisfaction survey.

6. Personnel/Organizations Responsible for Design, Collection, or Analysis of the Information

The sampling design specifications, specifications for data collection, questionnaire content, and data production are under the supervision of RITA/BTS. RITA/BTS is solely responsible for the review of final survey questionnaires, data, and technical documentation. The point-of-contact at RITA/BTS is:

June Taylor Jones, 202-366-4743

RITA/BTS

East Building-Room E32-338

1200 NJ Ave, SE

Washington, DC 20590

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