Video Transcript
Consider the descending
cumulative frequency graph shown, which represents the weights of 200
people. How many of the people weigh
more than 60 kilograms?
We recall that a descending
cumulative frequency of a value 𝑥 indicates the frequency of values that are
greater than or equal to 𝑥. Given the curve, we can use
this to find the number of people who weigh more than 60 kilograms. We draw a vertical line from 60
kilograms on the 𝑥-axis until it meets the curve, and then we draw a horizontal
line from this point to the 𝑦-axis. We can observe that the value
on the 𝑦-axis is 150. Hence, we can give the answer
that 150 people weigh more than 60 kilograms.
We know that the graph of a
descending cumulative frequency for a value 𝑥 gives us the frequency of values
that are greater than or equal to 𝑥. We have learned how we can plot
a descending cumulative frequency curve to show a distribution. However, we can also use a
descending cumulative frequency diagram to give us information about a data set,
not only for the values of the coordinates that we plot, but also for other
values that lie on the curve, as shown. Using our knowledge of how to
interpret a descending cumulative frequency graph, we will now see how we can
compare two data sets using their descending cumulative frequency graphs.
