Data collection for August 2000 Omnibus Household Survey began on August 9, 2000, at 1:00 p.m. EST and continued until August 21, 2000. Approximately 70 interviewers were trained for the study. Data were collected from households in the U.S. using a random-digit-dialed telephone survey method. The final data set includes 914 completed cases and a total of 209 variables. Battelle collected the data under contract with the Bureau of Transportation Statistics.
For this survey, 16,000 telephone numbers (in replicates of approximately 500) were purchased from Marketing Systems Group's (Ft. Washington, PA) GENESYS Sampling System. Of these, 9,990 were identified as working, residential telephone numbers that were released for use by the telephone interviewers. For this survey, the total number of telephone numbers in the sampling frame was 246,870,500.
The procedure for response rate calculation is based on the guidelines established by the Council of American Survey Research Organizations (CASRO). The final response rate for the survey was obtained using the following formula:
Distribution of household telephone numbers by disposition categories is presented in Table 1 below. The number of household cases in each category was then used in the above formula to calculate an overall response rate of approximately 16 percent.
Table 1. Distribution of Household Cases by Disposition Code
|Number of Telephone Numbers Released||9,990|
|Number of Pending Cases (Number not Dialed)||10|
|Number of Household Cases Worked||9,980|
|Number of Out of Scope Numbers (ineligible)||620|
|Number of No Contact (Scope Undetermined)||3,468|
|Number of Household In scope||5,892|
|Number of Complete Household Interview||914|
|Number of Language Problem||182|
|Number of Refusal||2,488|
|Number of Parental Refusal||7|
|Number of Unavailable During Study Period||2,301|
|Household Response Rate||10.1%|
Follow-up efforts were limited to six attempts to determine whether a telephone number was residential, an additional five attempts to identify an eligible respondent, and a final five attempts to secure a completed interview or refusal. Therefore, the maximum number of call attempts to any household was 16. Once contact was made with a household, follow-up attempts followed a loose call-back schedule established at the initial contact. That is, good times and days to call back were requested at the initial contact, but follow-up calls also were attempted before these appointment times, unless told otherwise not to do so by the household. This allowed for making the maximum number of attempts within the study period.
Prior to the start of actual data collection, a pretest was conducted to test the usability of the survey instrument. Particular focus was placed on testing questions that were new to the August survey. Qualified data collection and data preparation staff performed this pretest by first reviewing the questionnaire and then using it in simulated data collection situations. They looked for vague or confusing instructions, inconsistent questions or answer categories, incomplete or redundant sections, and poor pace, tone, flow, and format of questions. They also tested the interview length and determined that the survey questionnaire could be administered in approximately 20 minutes.
No pre-contact letter was mailed for the August survey.