Types of Sampling - Maths

What are the types of sampling techniques?

Simple random

Systematic

Stratified

Quota

Convenience

Simple random

Randomly select from population 

• Useful when you have a small population or want a small sample (such as children in a class)

• It can be time-consuming if the sample or population is large

• This can not be used if it is not possible to number or list all the members of the population (such as fish in a lake)

Systematic

A sample is formed by choosing members of a population at regular intervals using a list

• Useful when there is a natural order (such as a list of names or a conveyor belt of items)

• Quick and easy to use

• This cannot be used if it is not possible to number or list all the members of the population (such as penguins in Antarctica)

Stratified

The population is divided into disjoint groups and then a random sample is taken from each group

• Useful when there are very different groups of members within a population

• The sample will be representative of the population structure

• The members selected from each stratum are chosen randomly

• This cannot be used if the population can not be split into groups or if the groups overlap

Quota

The population is split into groups (like stratified sampling) and members of the population are selected until each quota is filled

• Useful when collecting data by asking people who walk past you in a public place or when a sampling frame is not available

• This can introduce bias as some members of the population might choose not to be included in the sample

Convenience

A sample is formed using available members of the population who fit the criteria

• Useful when a list of the population is not possible

• This is unlikely to be representative of the population structure

• This is likely to produce biased results