It also shows 4 different quartiles to let the teacher know the lowest, average, and highest grades the class is in. This graph also shows how spread out the data is on the line number. After drawing the box and whiskers for this data, you can see that the lowest grade is 35, the average grade is 78, and the highest grade is 86. The 67 to 86 box indicates that most students fall into that 'interval on their test. The disadvantage of this graph is that, like the other two graphs, it is not possible to see the individual test