The cumulative frequency curve above represents the percentage test scores of 100 students on a test
Finding the Median:
From the Y axis we can see that there is a total of 100 students in the sample. To find the median we must half the total number in the sample which gives 50. We then find the percentage mark relating to 50 on the x axis, this gives 60%.
Therefore the median mark is 60%
Finding the lower and upper quartile:
For the lower quartile we find ¼ of the total students, this gives 25 and for the upper quartile we find ¾ of the total students, which gives 75. We then find the percentage mark relating to 25 and 75 on the x axis, which gives 45% and 75% respectively.