Math Help Forum: box plot

Hi, this is my question:

The box plot shows the marks of 40 students in a maths test.
Two students scored the lowest mark of 3.

A) Use the box plot to draw a cumulative frequency diagram for the marks of the 40 students.

i have no idea how to do this with only the box plot, please help, thanks.

Hello,

In the rectangular, the first line (15) is the first quartile (the cumulative density function has value 0.25). The medium line (25) is the median (the cdf has value 0.5). The last line (32) is the third quartile (the cdf has value 0.75)
This already gives you an idea of the shape of the cdf !

The extremeties of the moustaches (horizontal lines) correspond to the extremal values