Mean, variance and standard deviation and their formula

Mean is the average of the data points.

Mean= Sum of all data points/( number of observations)

Variance describes how much a random variable differs from its expected value(mean) in other words variance is defined as the average of the squares of the differences between the individual (observed) and the expected value.

Variance = ∑ (xi-mean)2

n(number of observations)

The SD is a measure of how spread out numbers is in data. The square root of the variance is the standard deviation.√variance