Inter-quartile range, cumulative frequency, box and whisker plots - Higher
It is often better to display data in a table. This section will look at different ways to organise data, and revise the following terms:
The table shows the number of people on 12 different buses. Discrete data is normally grouped in the following way:
|Number of people on a bus||4-6||7-9||10-12||13-15|
From the table we can see that there were 7 buses with 7-9 people on them. But we have no way of telling exactly how many people were on each bus.
Now look at the class widths: they are all 3.
The midpoints of the classes are 5, 8, 11 and 14, as shown in red.
There are many ways to represent continuous data in a table.
This table shows the heights (h) of 25 people. The class widths are all 10.
120 h <130
130 h <140
140 h <150
150 h <160
The class boundaries are 120, 130, 140, 150 and 160.
The midpoints of the classes are 125, 135, 145 and 155, shown in red.
This table looks very similar to the table in example 2, and you might assume that the class boundaries are 20.5, 30.5 etc - but they are not! Remember that if you are 16 now, you will be 16 right up until your 17th birthday.