# Statistics - Standard Deviation

Standard deviation is the square root of the average of squared deviations of the items from their mean. Symbolically it is represented by ${\sigma}$.

We're going to discuss methods to compute the Standard deviation for three types of series:

## Individual Data Series

When data is given on individual basis. Following is an example of individual series:

 Items 5 10 20 30 40 50 60 70

## Discrete Data Series

When data is given alongwith their frequencies. Following is an example of discrete series:

 Items Frequency 5 10 20 30 40 50 60 70 2 5 1 3 12 0 5 7

## Continuous Data Series

When data is given based on ranges alongwith their frequencies. Following is an example of continous series:

 Items Frequency 0-5 5-10 10-20 20-30 30-40 2 5 1 3 12