Variance and Standard deviation are measures of data dispersion, they indicate how spread out a data distribution is.
A low standard deviation means that the data observations tend to be very close to the mean. while a high standard deviation indicates that the data is spread out over a large range of values.
Variance is the average of the squared differences from the mean, it gives us a very general idea of the spread of our data. A value of zero means that there is no variability; All the numbers in the data set are the same.
Varience = 1/N * SUM( (xi – X) 2) ::: X = Mean, N= Number of items in the sample
Standard Deviation –
The square root of the variance is the standard deviation. While variance gives us a rough idea of spread, the standard deviation is more concrete, giving you exact distances from the mean.
Standard Deviation = SQRT (varience)