Calculation of Standard Deviation

In the discrete series, when deviations are taken from actual mean, the formula is

Example:

From the following data, compute the value of standard deviations and variance.

Suggested answer:

Standard deviation from assumed mean method:

Step 1:

If a = assumed mean, then take the deviations of the items from a and call it d.

Step 2:

Step 3:

Multiply each fd by the corresponding d to get fd² and obtain S fd².

Step 4:

Note :

This method involves very less calculation than the deviation from actual method.