Beware of unseen errors

I’m a contrarian person by nature. I love writing about evidence that some common cultural narrative is wrong (or at least not the whole story). In particular, I’m fascinated by what kind of errors we are more likely to make.

In a world where headlines are driven by acute events, we are rather given to accusing the semi-innocent: monkey bars on playgrounds that lead to broken arms; bug parts in a can of Similac that could, in theory, make a baby sick; a side effect of a drug (that has other more beneficial effects).

But what about cases when we let the guilty go free? In logic, there is a kind of error called a “Type 2 error” that involves accepting the null hypothesis when it should have been rejected. There is a common null hypothesis in our cultural narrative that “what is perceived as normal is the safest option” and “better safe than sorry” that leads to such errors. For instance:

• Playgrounds are made safer to avoid injuries. But because they’re so safe, they’re boring, and no kid over age 4 is willing to play on them. Kids get less physical activity, and watch TV with ads for junk food instead — leading to long-term harm.

• Similac issues a recall because of bug parts found in a few cans of formula (incidentally, bug parts exist in lots of different items — there are guidelines for how many there can be). A parent learning this straps her three kids into the minivan and drives 10 miles per hour over the speed limit on the freeway to bring the can back to the store. She walks her three kids across the parking lot, thus exposing them to more risk than the potential of (generally harmless) bug parts in a few cans out of thousands made.

• In the wake of a plane crash, people choose to drive instead of fly. But cars kill roughly 1 out of 10,000 Americans per year — driving is one of the riskiest things we do.

• Pregnant women were once told to “take it easy” since it seemed like exercise could harm the baby. But it turns out that failing to exercise during a normal pregnancy leads to worse outcomes for mom and baby. Women who don’t exercise are more likely to gain excess weight. Excess weight is hard to lose, and carrying around excess weight over time leads to increased risk of cancer, heart disease, etc.

• People install residential alarm systems so the police will come fast in the event of a break-in. But an excess of false alarms so consumes police time that they have less time to combat crime that does exist — making everyone less safe.

I’d love to hear examples of other such errors.

Photo courtesy flickr user Florin Gorgan