16 Cumulative Frequency Worksheet Page 6
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27MEP Y9 Practice Book B
16.2 Grouped Data
When dealing with grouped data it is important to think about the type of data that
is being processed. You also have to decide the range of values that each group
contains.
When calculating the mean of grouped data, we assume that all the values lie at
the midpoint of the group.
These ideas are illustrated in the following examples.
Example 1
The table below shows the times taken by a group of walkers to complete a
15-mile walk. Their times have been recorded to the nearest hour.
Illustrate the data using a bar chart and a frequency polygon.
Time (hours)
3
4
5
6
7
8
Frequency
2
5
12
11
4
3
Solution
1
A time of 5 hours actually means a time that is greater than or equal to
4
hours
2
1
but is less than
5
hours, so the bar representing this time on the bar chart will
2
begin at 4.5 and end at 5.5.
Similarly, the bar for a time of 3 will begin at 2.5 and end at 3.5.
The bar chart is shown below:
Frequency
12
11
10
9
8
7
6
5
4
3
2
1
0
0
1
2
3
4
5
6
7
8
9
10
Time (hours)
173
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