Dear Shahzad, The iInter Quartile Range method uses a range of values, defined with the help of first and third quartiles, to identify the Outliers. The formula make use of two values termed as Low fence and High fence values, beyond which any value lying is considered as an Outlier.
Inter Quartile Range = IQR = (Q3 – Q1)
Where Q3 is the 3rd Quartile and Q1 is the 1st Quartile
Low Fence value = LF = Q1 – 1.5 * IQR
High Fence value = HF = Q3 + 1.5 * IQR
It is assumed here that the maximum value in any given set of data is within 1.5 times of IQR distance from Q3. So, also, the minimum value is at the distance of 1.5 times of IQR from Q1.
For more details, please see the following two research papers:
Ramnath Takiar (2023):The Relationship between the SD and the Range and a method for the Identification of the Outliers, Bulletin of Mathematics and Statistics Research, Vol. 11(4), 62-75.
Ramnath Takiar (2023):A New Method to Identify the Outliers Based on the Interquartile Range, Bulletin of Mathematics and Statistics Research, Vol. 11(4), 103-114.
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