Test scores for a class of 20 students are as follows:
93, 84, 97, 98, 100, 78, 86, 100, 85, 92, 72, 55, 91, 90, 75, 94, 83, 60, 81, 95
Test
Scores
Frequency
91-100
81-90
71-80
61-70
51-60
a) Copy and complete the table shown at the left.b) Find the modal interval.
The "modal interval" is the interval containing the greatest frequency. It is not the mode.
c) Find the interval that contains the median.



Solution:



Test Scores Frequency
91-100 9
81-90 6
71-80 3
61-70 0
51-60 2
20 total
b. 91-100 is the modal interval. This interval has the most data.
c. The middle of 20 is 10.

If I count from
the top, 10 will fall in the interval 81-90.
If I count from the bottom and go up, 10
will fall in the interval 81-90. The
interval that contains the

median is
81 - 90.