Reading Cumulative Frequency Curves
LESSON 1
The graph shows the cumulative frequency curve for the ages of 60 employees.
Use the graph to estimate
(a) the median,
(b) the interquartile - range.
Video Solution
Specified Values
To determine a specified frequency:
Locate the indicated value on the horizontal axis.
From this value, draw a vertical line upward to the cumulative frequency curve.
From the point of intersection between the vertical line and the curve draw a horizontal line to the vertical axis.
Read off the corresponding frequency from the graph.
If the required frequency is less than (at most) then the value from STEP 4 is the required value.
If the required frequency is more than (at least) then the value from STEP 4 must be subtracted from the total frequency.
LESSON 2
A group of 300 students of similar ability took an equivalent test. The following graph shows a distribution of their times.
(a) Determine the number of students who took at most 78 minutes to complete the test.
(b) Calculate the percentage of students who took at least 95 minutes to complete the test.
(c) Determine the probability that a student selected at random took between 80 and 90 minutes to complete the test.