People don´t understand probabilities.
“When people hear these analyses, however, they are not reassured but become more fearful than ever — they hadn’t realized there are so, many ways for something to go wrong! They mentally tabulate the number of disaster scenarios, rather than mentally aggregating the probabilities of the disaster scenarios.
–Steven Pinker, Blank Slate
I think generally people don´t understand numbers, period.
Good example is the probability of someone becoming a NBA player. The odds are naturally low, but there is a good indicator that increases the probability. That indicator is height.
For a man between 6 feet to 6”2”, the chance of being in NBA is five in a million.
At 6”2” to 6”4”, the chances improve slightly to 20 to million.
Man between 6”10” and 7 it is 32000 in a million (3.2%).
And for men over 7 seven feet tall, 17% of them are in the NBA right now*. So every six guy over 7ft you would encounter would be NBA player. Because massive growth is quite often attributed to some disease, it is even more likely that healthy seven-footer is a NBA player. So with narrowing the group, we have actually find quite a good indicator of your probabilities of becoming NBA player.
It is always important to go beyond the numbers.
Even the short NBA players are not really that short. Nate Robinson is only 5”7”, but his wingspan is 6”1”. NBA players in general have almost double more wingspan than regular people. Generally it is really rare that a player has shorter wingspan than his height. Yao Ming was one of them, but on the other hand he was 7”6”. So if you would need to predict someone´s ability to be a NBA player and you would need to rely only on two data points: height and wingspan would be probably the best with the former being more important.
*Stats read from a great book by David Epstein: The Sports Gene.