Skewness of frequency distribution — Statistics STD 11 Commerce — Question
Gujarat BoardEnglish MediumSTD 11 CommerceStatisticsSkewness of frequency distribution3 Marks
Question
Write a short note on Bowley’s method of finding the coefficient of skewness.
✓
Answer
Bowley's method: Base :
In a skewed frequency distribution. both quartiles $Q_1$ and $Q_3$ are not equidistant from the median $M$.
Measure of skewness:
Using the distances of quartiles from median, i.e., $\left(Q_3-M\right)$ and $\left(M-Q_1\right)$, the measure of skewness $S_k$ is obtained as follows :
$S_k=\left(Q_3-M\right)-\left(M-Q_1\right)$
$=Q_3-M-M+Q_1$
$S_k=Q_3+Q_1-2 M$
Relative measure of skewness :
Dividing the absolute measure of skewness by the sum of distances $\left(Q_3-M\right)$ and $\left(M-Q_1\right)$. the relative measure of skewness - the coefficient of skewness $(j)$ is obtained, i.e.,
If distances $\left(Q_3-M\right)$ and $\left(M-Q_1\right)$ are positive, then their difference may be less than or equal to their sum. Hence, $|j| \leq 1$, i.e., $-1 \leq j \leq 1$.
This method is used when we have to compute the skewness by using positional average.
This is the only method to calculate skewness when the frequency distribution has open-end classes.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.