Abstract of the book. The Organized Mind: Thinking Straight in the Age of Information Overload

Get to grips with probabilities or lose a vital skill for assessing information.

Imagine you’re at a university where ten percent of students are engineers. Look, here comes a student wearing a pocket protector: a plastic sheath for holding pens in your shirt pocket. Now, what would you say is the probability that this is an engineering student?

The fact that a pocket protector is a standard accessory for the stereotypical nerdy student might cause many of you to think he very likely studies engineering. But remember the ten percent ratio. If 90 percent of students aren’t engineers, it’s far more likely that our pocket-protector friend doesn’tstudy engineering.

Our initial misconception reflects the way in which a person or situation that seems a perfect example of something can cause us to ignore the base rate. A base rate is the probability of an event occurring without taking other factors into account.

Because of this tendency, it’s vital that we critically assess the way in which statistics are presented to us. After all, many of our important decisions may involve statistics, so our understanding of them should be unbiased.

Imagine that you’re very sick. Your doctor offers you a treatment that will increase the likelihood of your recovery by ten percent. If the treatment increases your likelihood of recovery from zero to ten percent, then you’ll still have little chance of survival. But, if it increases from 90 percent to 100 percent, your recovery is guaranteed, and you’ll certainly be on board!

What if it increases from 20 percent to 30 percent? You might hesitate and inquire about the side effects and cost of the treatment before agreeing.

From a statistical perspective, this is bizarre since in all of these cases, the increase of ten percent is the same. The scenarios just feel different because of their varying starting points.

Though our brains often have difficulty dealing with probabilities, by remembering the mathematics behind them, we can make our choices with a greater and more objective understanding of their implications.