Methods of calculation of standard deviation
a.Calculation of Standard Deviation - Individual Series: There are two methods of calculating standard deviation in an individual observation or series
a.Deviation Taken from Actual Mean: This method is adopted when the mean is a whole number of an even number . the followings are the steps.
1.Find out the actual mean of the series (x¯ ) .
2.Find out the deviation of each value from the mean ( X - x¯)
3.Square the deviations and take the total of squared devotions∑ X^{2}.
4. Divide the total (∑X^{2}) by the number of observations. The square root of the quotient is standard deviation. Thus apply the following formula:
= √∑X^{2}/ N or √ ∑ (X- x¯ )/ N