year 8 maths

524 Chapter 9 Data collection, representation and analysis
Example 1
Classifying variables
Classify the following variables as categorical, discrete numerical or continuous numerical.
a the gender of a newborn baby
b the length of a newborn baby
SOLUTION
EXPLANATION
a categorical As the answer is ‘male’ or ‘female’ (a word, not a
number) the data is categorical.
b continuous numerical
Length is a measurement, so all numbers are
theoretically possible.
Example 2
Collecting data from primary and secondary sources
Decide whether a primary source or a secondary source is suitable for collection of data on each of the
following and suggest a method for its collection.
a the average income of Australian households
b the favourite washing powder or liquid for households in Australia
SOLUTION
EXPLANATION
a primary source by looking at the census data The population census held every 5 years in
Australia is an example of a primary data source
collection and will have this information.
b secondary data source using the results from
a market research agency
A market research agency might collect these
results using a random phone survey. Obtaining
a primary source would involve conducting the
survey yourself but it is unlikely that the sample
will be large enough to be suitable.
Exercise 9A
UNDERSTANDING AND FLUENCY
1–5 3–6
4–6
1 Match each word on the left to its meaning on the right.
a Sample A only takes on particular numbers within a range
b categorical B a complete set of data
c discrete numerical C a smaller group taken from the population
d primary source D data grouped in categories; words like ‘male’ and ‘female’
e continuous numerical E data collected first hand
f population F can take on any number in a range
Cambridge Maths NSW
Stage 4 Year 8 Second edition
ISBN 978-1-108-46627-1 © Palmer et al. 2018
Cambridge University Press
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