What is standard deviation?

Question

it is part of statistics

Answer 1

This is a maths related question and this is a coding related questions place.
However, the standart deviation is a number that indicates how near are all the numbers of a sequence in general to the arithmetic mean of that sequence.
You can google it. They explain it better than me😅.

Answer 2

Mean and standard deviation are the most basic metrics for a distribution. The mean means ;) an average value, while standard deviation is how the distribution is spread out.
It is calculated as a square root of variance, which, in turn, is an average of squared differences (distances) of all the numbers versus the mean.

Answer 3

In a bell curve shaped distribution, a standard deviation is the level at which approximately 2/3 of things happen. 95% occur within 2 standard deviations. This is commonly used in finance in the following way - the stock market has an expected return of 8% with a standard deviation of 17%. So, in 2 out of 3 years, the returns for the stock market should return between +25% (8+17) and -9% (8-17). 95% of the time, returns in a given year should be between 43% and -26%. A year in which stock returns fall more than 26%, therefore, would be greater than a 2 standard deviation event - or worse than a 1 in 20 event.