## Content description

Investigate techniques for collecting data, including census, sampling and observation (ACMSP284)

Explore the practicalities and implications of obtaining data through sampling using a variety of investigative processes (ACMSP206)

### Elaborations

- identifying situations where data can be collected by census and those where a sample is appropriate
- investigating the uses of random sampling to collect data

Source: Australian Curriculum, Assessment and Reporting Authority (ACARA)

#### Population

An investigator usually wants to generalise about a whole class of individuals or objects. This class is called the **population**. Consider the following examples.

- A cure for a particular disease has been found to work for one group of patients and the investigator wishes to conclude that it will work for all similar patients. The population is the class of similar patients.
- A student investigator wants to find out which AFL team has the most supporters at their school. The population is the school's students and teachers.
- The most popular phone in a student's class is the Apple iPhone. The student investigator wants to find out if this is the most popular phone for students at their school. The population is the school's students.
- Sally is left-handed. She wants to find out what percentage of students at her school are left-handed and surveys the students in her class. The population is the school's students.

In studies designed to generate data, populations are generally thought of as being stable and unchanging. This allows researchers to make inferences about a population based on the data from a study because they assume that the population has not changed over the course of the study.

#### Example

A survey was conducted to discover which important literacy skills Australian year 8 students had developed. What is the population?

#### Solution

The population is all year 8 students in Australia.