Definition: Boxplot(or Box-and-Whisker plot) is one of the most effective graphical summaries of a data
set that provides a 5-number summary of the most effective graphical data(min, max, Q1,Q3,median)
and information about outliers.
Ex: The midday temperature (in °C) for 13 cities around the world are:
13 19 7 30 27 36 11 46 10 5 8 40 15
First put the data into order and then locate the median, LQ and UQ
5 7 8 10 11 13 15 19 27 30 36 40 46
In this the median value is nothing but the middle value because the sample points are odd in number.
If suppose they are in even number then we find the median from the average of the 2 middle values.
So here, the median is=15
Lower Quartile(Q1)= .25*no.of elements=0.25*13=3.25
That is 4th position of the elements=10
Upper Quartile(Q3)=0.75*no.of elements=0.75*13=9.75
That is 10th position of the elements=30