Question

how do you find the mean on a cumulative frequency graph?

Answer 1

We couldn't find directly mean from the cumulative frequency graph. If we divide the cumulative frequency curve into quarters, the value at the lower quarter is referred as lower quartile, the value at the middle is the median, and the value at the upper quartile gives upper quartile.

For finding mean, we have to find frequencies from the cumulative frequencies on the graph ( substrate value from the previous value). In this way we got frequencies for a given values of random variable say X,

Then calculate mean by using formula $\sum fi\, xi\, / \sum fi\,$

from example you will get idea about the mean,

for example frequency Cumulative freque requen to x 7.5 12.5 17.5 22.5 27.5 class limits 5-10 .. 10 15 15-20 20-25 25-30 5 S 30 20 10 60 Efiz60 Cumulative Frequency + 0 5 10 is 20 25 30 X Mean = Efixi - i=1,2,3,4,5 = 1125 mean = 18.75

In above formula,take product of X and f column and then take sum for the numerator and take sum of f column in denominator.