Producing Data

3. Sources of data

3.2 Generating your own data

3.2.2. Generating data from observations

iii. Sampling a population

Sampling a population might seem like an easy thing to do. However, sampling in a way that allows you to obtain the information that you need to answer your questions confidently can be more difficult. As an analogy, if you were buying fruit from a supermarket, would you chose only the fruit from the front of the tray, or would you examine (sample) the fruit from the middle and back of the tray to ensure that your population, i.e. all the fruit in the tray, was fresh?

Examples of sampling processes that are part of our everyday lives include:

• Public opinion polls. These are usually conducted to find out public opinion about a variety of issues. The population is made up of Australian residents who are over 18, and usually a sample of between 400 and 2500 people is interviewed.
• Market research. Market research is designed to learn about consumer preferences. Television ratings are an example of market research. Ratings indicate the proportion of the viewing public that watches a particular programme, which in turn influences the cost of advertising during the programme.

Engineering students who are working on designs of innovative products often find out about the market potential of a design by conducting some market research.

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