Study Design

The 2003 Motor Vehicle Occupant Safety Survey (MVOSS), like the baseline Motor Vehicle Occupant Safety Survey in 1994 and its follow-up surveys in 1996, 1998 and 2000, was conducted by telephone. Hence, the study procedures called for the construction of a national sampling frame of telephone households from which a random population sample could be derived. For each of the two survey instruments (one focusing on safety belts and the other on car seats, with a common core of questions relating to personal characteristics and driving behaviors), a national probability sample was developed. Each sample was composed of approximately 6,000 persons age 16 and older, including over-samples of persons age 16-39. Since the sampling procedures and data collection methodology for the two samples were identical, procedures described in this report for one sample apply to the other as well.

The procedure for developing a population-based sample for this telephone survey involved four stages. The first stage sample involved using a population-based sample allocation, distributed in proportion to the geographic distribution of the target population according to the most recent Census estimates. The second stage employed a systematic selection of assigned telephone banks within the geographically stratified first stage sample design. The third stage used a random digit dialing (RDD) sampling of telephone households within the telephone banks selected in the second stage. The fourth stage required the identification and systematic selection of one eligible respondent within each sampled household so that the household sampling frame yielded a representative sample of the eligible population. These procedures yielded national estimates of the target population, within specified limits of expected sampling variability, from which valid generalizations can be made to the general public. The sampling procedures used to develop the sample for the 2003 surveys were the same as those used to draw the sample for the 2000, 1998, 1996 and 1994 surveys.

The two primary differences in study methodology between the 2000 MVOSS and the current survey were a change in the field period from November-January to January-March and an increase from a 5-call design to a 10-call design. The new field period for the 2003 MVOSS permitted results to be reported in the same calendar year as the data were collected. There was no reason to expect that the survey results would be affected by this change. The extended call design increases the likelihood of including younger and more mobile respondents, who are less likely to be at home and reached in a five call design. The extended call design also permitted the incorporation of answering messages referring not-at-home respondents to the SRBI toll-free number to conduct interviews and the NHTSA website to confirm the authenticity of the survey.

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