Originally Posted by
DaveReidUK
An equally valid question would be why ability (at anything, not necessarily confined to piloting) should be assumed to follow a normal distribution (normal in the mathematical sense, i.e. symmetrical about the mean/median/mode).
It's perfectly possible that the ability distribution is actually skewed, in other words the peak isn't halfway between the two extremes, so that for example there could be a concentration of pilots towards the upper end of the ability scale.
Or, perish the thought, the lower end.
Well, first of all, it doesn't really matter. The whole argument still stands, even if the distribution is skewed. Worse even, if it's skewed, then you have either some really, really bad pilots out there, or most pilots are below average, with a few aces flying around. Which one would you choose ;-)?
But in reality, it's very likely very close to normal. Take an example: how is the height of NBA players distributed? We pick the best, tallest athletes from the whole population, for sure they will all be best of the best, right? There are just 500 NBA players, out of the population of 300,000,000, that's top 0.000167%. For sure their height can't be normally distributed??
Well, spoiler alert, their height is basically normally distributed.
Ok, actually this is showing % of minutes played by different heights, so one could expect it to be even more skewed, but it's not.
And that's just 500 players. There are 600x more airline pilots, and with the sample size like that, the distribution is going to be normal.