Drug driving again
Three sentences from a Herald story
The Ministry of Transport study used blood samples taken from 453 drivers who caused crashes.
Of that group, 156 were found to be on drugs not administered by a medical professional
Drivers with more than the legal limit of alcohol in their system made up just over half of the 453 samples analysed.
Now try to fill in the blank in the headline “Tests reveal most crash drivers “
If you said “were drunk”, your arithmetic is better than your sense of headlineworthiness, not a problem the Herald had.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »
Original report at: http://www.transport.govt.nz/research/othertransportresearch/Documents/Drug-Research-Report-2012.pdf
258/453 drivers had drugs in their blood samples, more than half, 102 of these people MIGHT have been prescribed the drug in question
12 years ago
Actually, the report distinguishes people who might have been prescribed the drug in question after the crash — they didn’t try to separate drugs prescribed before the crash from unprescribed ones, and there’s a small number that probably were.
More to the point, it’s pretty obvious that some of the drugs were given after the crash, otherwise you wouldn’t get twice as many people testing positive for opiates as for cannabis. A recent US report that looked at fatally-injured drivers responsible for crashes and that didn’t have the hospital contamination problem found twice as many testing positive for cannabis as opioids, and cannabis use is less common in the US than here.
Even if you believe that a substantial majority of the opiate findings were pre-crash use (which is what it would take to make the headline technically correct), there’s still the point that a positive test implies recent use , not current impairment. Compare that to the more-than-half with blood alcohol over the legal limit who were pretty clearly impaired to some extent, and I still think the headline is misleading.
12 years ago
PS. Thanks for the link.
12 years ago