Page 2 - LESSON NOTES

Mean deviation for continuous frequency distribution

where xi are the mid-points of the classes, [latex s=1]\bar { x }[/latex] and M are respectively, the mean
and median of the distribution.

Variance
Variance is the arithmetic mean of the square of the deviation about mean [latex s=1]\bar { x }[/latex].
Let x1, x2, ……xn be n observations with [latex s=1]\bar { x }[/latex] as the mean, then the variance denoted
by σ , is given by
2

Standard deviation
If σ is the variance, then σ is called the standard deviation is given by
2

Standard deviation of a discrete frequency distribution is given by

Standard deviation of a continuous frequency distribution is given by