population, census & sample

The population is the entire group under investigation. This is also referred to as the target population.

eg All 150 Year 9 students at ABC College.

eg All trout in Lake Taupo

A census is a survey to collect data or information from the entire population.

eg All 150 Year 9 students at ABC College.

eg Catching every single trout in Lake Taupo

A sample is where we use a part or subset of the population.

eg 20 out of 150 Year 9 students at ABC College.

eg Catching 10 trout in Lake Taupo

A sample should be large enough and collected in an appropriate way to represent the population.

A representative sample means the sample looks as close to the population as possible. This is also called a fair sample.

eg If a Scout group had 75% males, then a representative sample would be a sample that had as close to 75% males in the sample.

If the sample is not fair or not representative of the population, we call it a bias. This means to favour something during the selection process.

eg If a Scout group had 75% males, and we took  sample of this group which only had 50% male in the sample, we could say the sample is a bias sample.