Quartile deviation is also known as the semi-interquartile range, is a measure of statistical dispersion. It indicates the spread of the middle 50% of a dataset. The quartile deviation is calculated using the first quartile (Q1) and the third quartile (Q3). The formula is:

Quartile Deviation=𝑄3−𝑄1/2
Coefficient of Quartile Deviation = 𝑄3−𝑄1/𝑄3+𝑄1
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Here’s a step-by-step explanation:

Arrange Data: Organize the data set in ascending order.

Find Quartiles:
Q1 (First Quartile): The median of the lower half of the dataset (not including the median if the dataset has an odd number of observations).

Q3 (Third Quartile): The median of the upper half of the dataset (not including the median if the dataset has an odd number of observations).

Calculate Quartile Deviation: Subtract Q1 from Q3 and divide by 2.

The quartile deviation provides a robust measure of spread as it is not affected by extreme values or utliers. afterwards find coefficient of quartile deviation by formula QD = 𝑄3−𝑄1/𝑄3+𝑄1 you can watch the video for practical solution of this in various type of series like Individual Series , Discrete Series and Continuous Series. Here in this lecture you will find the Practical Solution in Discrete Series , kindly check the link here and do Subscribe to the channel :

Thanks a Lot
jatin