A cumulative frequency table shows the number of values that lie in or below a given interval. Start by identifying the minimum and maximum data values and defining the intervals.
Example Table:
Earthquake Magnitude
Frequency
Cumulative Frequency
2.1 - 4
7
7
4.1 - 6
4
11
6.1 - 8
1
12
8.1 - 10
1
13
Practice makes perfect
A cumulativefrequency table shows the number of values that lie in or below an interval. To make a cumulative frequency table, we will start by identifying the minimum and maximum data values.
Then we can define the intervals for each line of our table.
2.1, 5.4, 6.7, 3.2, 4.5, 2.7,
2.6, 3.1, 4.4, 8.1, 4.1, 2.9, 2.1
The minimum value is 2.1 and the maximum value is 8.1.
In this case, intervals of 2 seem reasonable. Let's list them in the first column of our cumulative frequency table.
Earthquake Magnitude
Frequency
Cumulative Frequency
2.1 - 4
4.1 - 6
6.1 - 8
8.1 - 10
Now, let's count the number of values in each interval.
2.1, 5.4, 6.7, 3.2, 4.5, 2.7,
2.6, 3.1, 4.4, 8.1, 4.1, 2.9, 2.1
Looking at the data, we can see that there are 7 values in the first interval, 4 values in the second interval, 1 value in the third interval and 1 value in the fourth interval. Now we can complete the second column of our table.
Earthquake Magnitude
Frequency
Cumulative Frequency
2.1 - 4
7
4.1 - 6
4
6.1 - 8
1
8.1 - 10
1
Finally, for the last column we add the frequency of each interval to the frequencies of all the previous intervals. We will do this by adding the frequency of each interval to the cumulative frequency of the previous interval.
