The box plot or box and whisker diagram is a standardized way of displaying the distribution of data based on the five number summary: minimum, first quartile, median, third quartile, and maximum. In the simplest box plot the central rectangle spans the first quartile to the third quartile (the interquartile range or IQR). A segment inside the rectangle shows the median and "whiskers" above and below the box show the locations of the minimum and maximum.

Example:- Data = 11,13,13,15,15,16,19,20,20,20,21,21,22,23,24,30,40,45,45,45,71,72,73,75

For plotting box plot divide the given data in 3 segments

First segment only contains median and other two segments will contain upper and lower part of median

median=21.5

upper segment =22,23,24,30,40,45,45,45,71,72,73,75

lower segment =11,13,13,15,15,16,19,20,20,20,21,21

Find out mean of each segment and mark it on graph as shown bellow and also mark actual median of data

median of upper segment =45

median of lower segment =17.5

plot the chart