How to calculate the length of whisker in a box plot?

box_plot

#1

I am currently studying about how to calculate the variability in the variable while studying it I found out that IQR(Interquartile Range )is one of the methods and we can visualize IQR by box plot.But In a box plot, I came across a doubt that how the length of the whisker is calculated in the box plot.


#2

I think it varies slightly from different packages. But in general, I have observed the following:

Lower Extreme = smallest value greater than Q1-1.5IQR
Upper Extreme = greatest value smaller than Q3+1.5
IQR

The following image might make things clearer:

K generally takes value 1.5 to 3. Once you know the points, calculating length is easy. Hope this helps.

Cheers,
Aarshay