## 4.1 Concepts of Population and Random Samples

#### Population and Samples

- The set of all eligible members of a group which we intend to study is called a population.

For example, if we are interested in the IQ scores of a secondary school’s students, then all students in this school is considered as a population; if we want to know the average IQ scores of all students in Australia instead, then this becomes the population.

- There are
**difficulties in dealing with a population**:

i) The population might be too large – e.g. there are too many students in Australia.

ii) The population may be hard to access – e.g. the blue whales in the Pacific Ocean.

iii) The data collection process might be destructive – testing all the batteries’ durability would mean to use up all the batteries to test, which is a waste.

- To solve these problems, we use a subset of the population – called a sample – instead, and hope that it can represents the true population.