Normal Distribution

There are 10 black stones and 10 white stones in your pocket. What is the distribution of the number of black stones when I take out 10 randomly?

Normal distribution

Gauss in Germany has done research on how much error is made when doing various experiments, and the result is announced as ‘law of error’. The distribution curve of this ‘law of error’ is ‘normal distribution’.
Normal distribution is the most commonly used distribution curve used as a statistical model. (Standard Deviation σ = 1)

Most phenomena occurring in nature are similar to normal distribution curves. For example, the height, weight, and IQ of a student in a classroom are known to form a normal distribution curve.
The average number of students is the highest, and the further away from the average, the fewer the number of students.  Distribution of male and female height between 25 and 29 (http://sizekorea.kats.go.kr/)

Note that the normal distribution curve is merely a mathematically derived curve. It is used as a mathematical model only if it is suitable for describing realistic data.