Cambridge International Mathematics

Analysis of discrete data (Chapter 13) 277

There are two types of variables that we commonly deal with: categoricalvariables andquantitative

variables.

Acategorical variableis one which describes a particular quality or characteristic.

It can be divided intocategories. The information collected is calledcategorical data.

Examples of categorical variables are:

² Getting to school: the categories could be train, bus, car and walking.

² Colour of eyes: the categories could be blue, brown, hazel, green, and grey.

We saw examples of categorical variables inChapter 5.

Aquantitative variableis one which has a numerical value, and is often called anumerical variable.

The information collected is callednumerical data.

Quantitative variables can be eitherdiscreteorcontinuous.

Aquantitative discrete variabletakes exact number values and is often a result ofcounting.

Examples of discrete quantitative variables are:

² The number of people in a household: the variable could take the values 1 , 2 , 3 , ...

² The score out of 30 for a test: the variable could take the values 0 , 1 , 2 , 3 , ..., 30.

² The times on a digital watch:

Aquantitative continuous variabletakes numerical values within a certain continuous range. It is usually

a result ofmeasuring.

Examples of quantitative continuous variables are:

² The weights of

newborn babies:

the variable could take any positive value on the number line but is likely to be in

the range 0 : 5 kg to 7 kg.

² The heights of

Year 10 students:

the variable would be measured in centimetres. A student whose height is recorded

as 145 cm could have exact height anywhere between 144 : 5 cm and 145 : 5 cm.

² The times on an

analogue watch:

In this chapter we will focus ondiscretevariables. Continuous variables will be covered inChapter 17.

INTERNET STATISTICS

There are thousands of sites worldwide which display statistics for everyone to see. Sites which show

statistics that are important on a global scale include:

² for the United Nations

² for the World Health Organisation

A VARIABLES USED IN STATISTICS [11.2]

12:1512:15

http://www.un.org

http://www.who.int

IGCSE01

cyan magenta yellow black

(^05255075950525507595)
100 100
(^05255075950525507595)
100 100
Y:\HAESE\IGCSE01\IG01_13\277IGCSE01_13.CDR Thursday, 25 September 2008 4:17:15 PM PETER