Cambridge International Mathematics

112 Graphs, charts and tables (Chapter 5)

When we construct a statistical investigation, we collect information calleddata.

There are several different types of data that we can collect:

Categorical datais data which is sorted into categories.

Numerical datais data which can be written in numerical form. It can either bediscreteorcontinuous.

Discrete data takes exact number values, and is often a result ofcounting.

Continuous data takes numerical values within a continuous range, and is usually a result ofmeasuring.

Graphs and charts are used to display data in a form that is not only more visually appealing, but also easier

to understand.

In this chapter we will look at different kinds of graphs and charts which can be used to both analyse and

compare data. In particular, we will see that categorical data is usually displayed using abar chartor apie

chart, and numerical data is usually displayed using aline graphor astem-and-leaf plot.

BAR CHART

Abar chartis a popular method of displaying statistical data and is probably the easiest statistical graph

to construct. The information may be displayed either vertically or horizontally. The height (if vertical) or

length (if horizontal) of each bar is proportional to the quantity it represents. All bars are of the same width.

If the data is discrete then the bars are separated by a space.

Example 1 Self Tutor

Mode of transport Car Bicycle Bus Walk

Number of teachers 15 3 7 5

Teachers at a local school were asked what

mode of transport they used that day to travel

to school. The results are summarised in the

table:

a Display the data on a vertical bar chart.

b What percentage of teachers used a bus that morning?

abTotal number of teachers

=15+3+7+5

=30

= 307 £100%

¼ 23 :3%

A STATISTICAL GRAPHS [11.3]

Vertical bar chart

4

2

6

8

10

Horizontal bar chart

268104

Percentage who used a bus

0

5

10

15

20

Car Bicycle Bus Walk

number of teachers

Mode of transport to school

IGCSE01

cyan magenta yellow black

(^05255075950525507595)
100 100
(^05255075950525507595)
100 100
Y:\HAESE\IGCSE01\IG01_05\112IGCSE01_05.CDR Wednesday, 8 October 2008 4:32:06 PM PETER