What is the Normal Distribution?
Normal is my father's name, please call me "Bell Curve"
If you’ve ever heard of a ‘bell curve’ or a ‘Z-score’ then you have been hearing about a Normal Distribution!
The last time we talked about probability distributions was when we talked about the Uniform Distribution last month!
If a Uniform distribution models situations where every outcome is equally likely then the Normal distribution models situations where the probability of possible outcomes corresponds to what tends to happen in nature.
Now that might seem a little vague, so some concrete examples of naturally occurring quantities that are distributed Normally are:
Heights of human beings
Weights of newborn babies
Age of Retirement
The key here is that there are three aspects to each of these quantities:
There is a single mean value that tends to dominate.
The average American man is 5ft 9in tall.
There is a balanced spread of variations around this mean.
You get very tall and very short men and everything else in between.
These heights are less common the further away you are from the dominant mean value.
There are no insanely extreme values.
You can meet a really tall man, but nobody is 10,000ft tall!
The Normal distribution is a good one to get familiar with, because it is very common in nature, and crops up for all manner of unexpected reasons, such in this video below!
We’ll be seeing the Normal distribution again. For now, just enjoy the show!