DRUG TEST ACCURACY RATES MISLEADING

In regards to the story concerning drug testing at Wurtland Middle School.
it should be noted that, when testing for drugs, a "99 percent reliability
rate" might not be what it first appears.

It may be that it means that 99 percent of those who actually took drugs
will test positive (a good result). It may not mean that 99 percent of those
who don't take drugs will test negative.

In fact, a high percentage of false positives can occur if the percent of
those who actually use the drug is fairly low. For example, if only 2
percent of the target population actually uses the drug and the test is
wrong 1 percent of the time (possibly due to over-the-counter medications,
certain foods, etc.), then it can be shown that about 33 percnt of those who
test positive will be false positives.

It would be very easy to penalize the innocent.

George Livingston

Ironton, Ohio