X̅ = A + ∑ d

X̅ = A + ∑ d n Introduction to Statistical Methods and Econometrics that it is the square–root of the mean of the squared deviation from the arithmetic mean. It provides accurate result. Square of standard deviation is called Variance. Definition: It is defined as the positive square- root of the arithmetic mean of the square of the deviations of the given observation from their arithmetic mean.

The standard deviation of the population is denoted by the Greek letter σ (sigma) The standard deviation of sample is denoted as 's' . Calculation of Standard deviation- Individual Series: There are two methods of calculating Standard deviation in an individual series. a) Deviations taken from Actual mean b) Deviation taken from Assumed mean Standard Deviation = ∑(x - x̅) n ቆ ቇ Where, x̅ = mean value of distribution n = number of observations. Steps: .

Find out the actual mean of given data ( X̅) . Find out the deviation of each value from the mean ( x ⁼ X – X̅ ) . Square the deviations and take the total . Divided the total ∑ x by the number of observation ቆ ቇ .

The square root of ቆ ቇ is standard deviation.