Reasons that potential case and control drivers were excluded from the study and reasons that the remaining potentially eligible case and control drivers were not interviewed or not used in the final analysis
| Potential cases (n=1521) | Potential controls (n=3227) | |
|---|---|---|
| NA = not applicable. | ||
| Reason for exclusion | ||
| Control higher in rank interviewed | NA | 2050 |
| Vehicle not registered in Washington | 258 | 210 |
| Motorcycle | 3 | NA |
| Driver younger than 18 years | 55 | 1 |
| Vehicle fire only | 12 | NA |
| Parked vehicle | 23 | NA |
| Vehicle fled scene or stolen | 6 | NA |
| Driver died | 10 | NA |
| Not sampled | 45 | NA |
| Total excluded | 412 | 2261 |
| Number potentially still eligible | 1109 | 966 |
| Reason no interview was obtained | ||
| Report received too late from patrol | 102 | 16 |
| Report not sent by patrol | 55 | NA |
| Owner name and address not found | 2 | 58 |
| Staff not available or staff error | 26 | 8 |
| No telephone number found | 234 | 187 |
| Unlisted telephone number | 81 | 62 |
| Disconnected telephone | 12 | 11 |
| No answer despite multiple calls | 34 | 48 |
| Answering machine only | 85 | 124 |
| Rental agency refused information | 5 | 10 |
| Commercial owner could not locate driver before deadline | 53 | 36 |
| Other reasons | 21 | 25 |
| Presumed owner denied ownership | 0 | 45 |
| Reached household member, not driver | 84 | 58 |
| Household member refused on behalf of driver | 24 | 8 |
| Driver denied crash or driving at reference time and location | 3 | 31 |
| Driver did not speak English | 8 | 2 |
| Driver refused interview | 54 | 34 |
| Total not interviewed | 883 | 763 |
| Number interviewed | 226 | 203 |
| Reason not used in analysis | ||
| Control license numbers not collected | 7 | NA |
| Controls collected at wrong time | 2 | 2 |
| Major errors in control interview | 2 | 2 |
| No control interviewed | 15 | NA |
| Included in final analysis | 200 | 199 |