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8 February 2012

Be careful reading the Flathead Beacon’s story on drug testing

Flathead Beacon reporter’s Dillon Tabish’s story More Flathead Employees Failing Drug Tests invites readers to conclude that the rate of positive test results is on the rise. That would be a mistake.

In fact, the figures provided in Tabish’s story reveal that the rate of positive results actually declined slightly in 2011. More tests scored positive in 2011 than in any year in the 2007–2011 era for which results were reported — but that’s because more people were tested in 2011 than ever before.

Although the rate of positive results is the the proper statistic for evaluating the trend over time, the results for each year are not completely comparable because different populations are tested. Therefore, the apparent trends in the graphs below may be spurious.

Graph 1 plots the percentage of positive results over time. Graph 2 displays the number of positive results as a function of the number of persons tested. The R-squared statistic is a rough indicator of how closely the variables are linked. The higher the R-squared, which has a range of 0–1, the closer the link.

 

What worries me most is not the number of positive results. The percentage of positives is holding steady or declining slightly. Yes, the number of positives is increasing, but that’s due to more people being tested.

It’s the large increase in the number of people being tested that I find troubling. Demanding a drug test when an employee can’t do his job because he’s slurring his words, can’t keep his balance, can’t touch his nose, or jitters around like a Mexican jumping bean that spent too much time at Starbucks, may be justified. But requiring drug tests as a condition of being hired, and of staying employed, throws away the presumption of innocence, taking us another step closer to a police state and another step away from the land of the free.