Innumeracy summary

It’s rare to hear people openly admit to illiteracy; yet it’s quite common to hear someone acknowledge that math was his worst subject, or shrugging and saying that he’s simply not a numbers person.

But innumeracy – that is, lacking the basic notions of math – is nothing to boast about.

Being innumerate has a host of negative consequences, one of them being an inability to react appropriately and make accurate judgments in circumstances involving numbers and probability.

An incapacity to determine whether a figure in a given context is big or small makes innumerates prone to personalizing, when their numerical intuition is prejudiced by their own experience.

For instance, the probability of being eaten by an alligator is quite low, although it does sometimes happen. But an innumerate person might read a news story about such an event and develop an irrational fear of alligators, ignoring any statistical evidence demonstrating that gator attacks are a very rare occurrence.

Another negative effect of innumeracy is the inability to grasp the implications of simple mathematical principles.

Let’s take the multiplication principle, which holds that if we have m different ways of making a choice and n different ways of making a subsequent choice, then we have m x n different ways to make these choices in succession.

To apply this elementary concept to an everyday situation, we would be able to conclude that a woman with five shirts and three pairs of pants would have 15 (5 x 3) outfit choices for any given day.

Going even further, the multiplication principle would yield the conclusion that if the woman were planning her outfits for an entire week, she would have 15 choices the first day, 15 the next day, and so on, or a total of 15⁷ choices – that’s 170,859,375 options!

Innumerate people, however, might reject the truth of this number and believe that it’s ridiculous that a few shirts and pants could result in such an incomprehensibly large number.