Sampling Methods

What is a target population?

The particular subgroup to be studied from which the researchers findings will be generalised from using a sample

What is a sample?

A smaller, representative group of a larger target population that can be used to generalise for the overall population

What are the types of sampling?

Random

Systematic

Stratified

Opportunity

Volunteer

What is random sampling?

When every member of the target population has a equal chance of being selected - involves identifying everyone in the target population then selecting the number of participants needed in a way which gives each participant and equal chance of being chosen e.g. names from a hat, unbiased computer name generating software

What are the strengths of random sampling?

No researcher bias - more representative so can be generalised

What are the limitations of random sampling?

Difficult and time-consuming to ensure all of the target population has a chance

Some participants might not want to take part so becomes more of a volunteer sample

What is systematic sampling?

A predetermined system to select participants e.g. giving people a number and choosing every nth person from the line, consistently continuing at that interval until the required amount of participants are chosen

What are the strengths of systematic sampling?

No researcher bias

What are the limitations of systematic sampling?

May not be truly unbiased - every nth person may share a characteristic, however this is unlikely - sample could not be representative so can’t generalise

What is stratified sampling?

Identifying subgroups in a population and choosing participants from each ‘stratum’ in proportion to their occurrence within the overall population e.g. 20 students, 18m and 2f, sample of 10, uses 9m and 1f for the sample as it is proportional and representative

What are the strengths of stratified sampling?

No researcher bias - random generation once strata have been identified

Representative so can be generalised

What are the limitations of stratified sampling?

Difficult and time-consuming to ensure the strata of the target population and properly identified

All strata identified cannot reflect all individual differences between those in the target population so true representation would be difficult to obtain

What is opportunity sampling?

Using anyone who is available and willing e.g. going into a supermarket and using the first 20 participants who agree to take part

What are the strengths of opportunity sampling?

Convenient and easy

Quick so also saves money

What are the limitations of an opportunity sample?

Bias - sample is from a specific location so has similar people

Increased researcher bias - who they approach

What is volunteer sampling?

Participants self-select by volunteering when asked or responding to an advert

What are the strengths of volunteer sampling?

Minimal effort - volunteers contact the researcher

Quicker and easier

What are the limitations of volunteer sampling?

Bias - particular type of person who volunteers

No representative so can’t generalise