Sampling

What is a target population?

The group the researcher is interested in studying

What is a sample?

A smaller group drawn from the target population who take part

Why do researchers use samples?

The target population is too large to study fully

What is a representative sample?

One that reflects the target population so findings can be generalised

What is bias in sampling?

Some groups are over or under represented

What is generalisation?

The extent findings can be applied to the target population

What is opportunity sampling?

Selecting whoever is available at the time and place

What is a strength of opportunity sampling?

Convenient and quick and cheap

What is a weakness of opportunity sampling?

Likely unrepresentative and biased by the researcher's choice

What is random sampling?

Every member of the target population has an equal chance of selection

What are the steps of random sampling?

List the population - assign numbers - use a random number generator (or names from a hat)

What is a strength of random sampling?

No researcher bias

What are weaknesses of random sampling?

Time consuming and needs a full list and may still be unrepresentative and people may refuse

What is systematic sampling?

Every nth member of the target population is selected

What is a strength of systematic sampling?

Avoids researcher bias and is quicker than random

What is a weakness of systematic sampling?

A hidden pattern in the population may coincide with the interval

What is volunteer sampling?

Participants self-select by responding to an advert

What is a strength of volunteer sampling?

Finds niche samples and is cheap

What is a weakness of volunteer sampling?

Volunteers are keen and helpful so demand characteristics and bias are likely

What is stratified sampling?

The population is divided into strata and participants are randomly selected from each in proportion

What is a strength of stratified sampling?

Representative and avoids researcher bias so generalisation is possible

What are weaknesses of stratified sampling?

Needs detailed knowledge and is time consuming and the researcher chooses the strata

Which sampling method is likely to be most representative?

Stratified

Which sampling method uses whoever is available?

Opportunity

A class is 90% right-handed - how many right-handed students are in a stratified sample of 10?

9

How many left-handed students are in that stratified sample of 10?