How do you estimate the mean and the quartiles from a cumulative frequency graph?

If the total frequency is 60

draw a line from the frequency axis at 30 to the curve. Draw a vertical line to the x axis and read off. This is the mean

for LQ do as above but at 15 and 45 on the frequency axis.

it is an estimate as you have drawn a curve and everyone’s will be slightly different

Typically with a cumulative frequency diagram you will be asked to find the median and the upper and low quartiles. The median is found by the total frequency which is value on the y axis of the highest part of the graph and dividing it by 2, draw a line across from that value on the y axis to the graph and then a vertical line down to the x axis to find the median value. For the lower quartile, divide the total frequency by 4. For the upper quartile, divide the total frequency by 4 and then multiply by 3.