Detailed sampling plans are available from survey final reports.[25], [26], [27], [28], [29], [30], [31], [32], [33], [34] In Table S1 we describe each survey along with sampling characteristics, response rates and eligible sample sizes.
From 1999 to 2002, a total of 25,316 people were included in the eligible sample, 21,004 people (83%) were interviewed, and 19,759 people (78% of the eligible sample) were examined.
The final eligible sample comprised 94 participants and 248 encounters at actively controlled crossings where a violation of the active warnings was possible.
Thirty eight participants had not been released from custody throughout the duration of the follow up period, so the eligible sample was reduced to 84 participants.
Results for the eligible sample are nearly identical to those listed in Table 3 when industry controls are excluded from those regressions.
Because participation rate tends to vary between different subgroups of the eligible sample (eg, it may be particularly low among young males), it influences the overall results (ie, is a source of bias).
This left an eligible sample of 9451.
The final eligible sample included 190 PCPs.
The final pre-contact eligible sample consisted of 250 physicians.
Response rates based on estimated eligible sample averaged 52.89%.
Full data were obtained for 589 (86.0% of the eligible sample).
