RM: sampling

What is a population?

A population is an entire group with specified characteristics

What is the target group/population?

The target group/population is the desired population subgroup to be studied and therefore want research findings to generalise too

Why are sampling methods used to choose a representative sample from the target group?

sampling methods are used because a target group is usually too large to study in its entirely

What is a rappresentative sample?

A rappresentative sample is a subset of the target group with similar distribution of the relevant characteristics which allows us to generalise from the sample to the target group

What is an unrepresentative sample?

An unrepresentative sample is one that does not reflect the distribution of characteristics of the target group and cannot be generalised to the target population and therefore biased

Why do we use sampling technique?

Sampling technique are used to produce a representative sample

Why do vast majority of samples lack population validity

Because vast majority of samples contain some degree of bias

What are the five sampling technique?

1. Random

2. Systematic

3. Stratified

4. Opportunity

5. Volunteer

Which sampling technique ensures that all members of the target population have an equal chance of being selected?

Random sampling

How is random sampling carried out?

• The researcher would create a list of all members of the target population

• Then he would assign a number to each member

• Generate the sample through the use of some lottery method (picking numbers from a hat)

What are the strengths of random sampling?

1. Free from researcher bias

2. More representative than some other sampling method

Why is random sampling free from researcher bias?

Random sampling is considered free from researcher bias because participants are selected entirely by chance, rather than being chosen based on the researcher’s preferences or judgment. This ensures that every member of the population has an equal chance of being included, reducing the likelihood that the sample is systematically biased.

what are weakness of random sampling?

1. Time consuming

2. May still be unrepresentative

Why may random allocation be time consuming

Random allocation may be time consuming because participants must be assigned to conditions purely by chance, ensuring true randomness and balanced groups, which requires careful planning and checking.

Why may random sampling still be unrepresentative?

Random sampling may still be unrepresentative because chance does not guarantee a representative sample; the sample may be biased by luck, an incomplete sampling frame, or a small sample size.

What is systematic sampling?

Systematic sampling is when every nth member of the target population is selected. For example every 3rd person.

What’s the process of systematic sampling?

For systematic sampling, a frame is produced which is a list of people in the target population organised into an order like alphabetical. A sampling system is then nominated or is determined randomly to reduce bias. The researcher then works through the sampling frame until the sample is complete.

What are the strengths of systemic sampling?

• fairly representative

• Avoids researcher bias

How does systematic sampling avoid researcher bias?

Systematic sampling avoids researcher bias because selecting participants using a fixed system (e.g., every nth person), so the researcher cannot influence who is chosen.

What’s a weakness of systematic sampling?

Time consuming

What is opportunity sampling?

Opportunity sampling is when the researcher decides to simply select anyone who happens to be willing and available at that time, like asking whoever is around at the time of the study

What are the strengths for opportunity sampling?

• it’s convenient

• It’s cost and time effective

What are the weaknesses of opportunity sampling?

• unrepresentative

• May be effected by researcher bias

What is volunteering sampling?

Volunteer sampling involves participants selecting themselves to be part of the sample

How is a volunteer sampling conducted?

For a volunteer sampling, a researcher may place an advert in a newspaper or on a common room notice board- or willing participants simply raise their hand when the researcher asks

What is the strength of volunteer sampling?

Less time-consuming than other methods

What are weakness of volunteer sampling?

• volunteer bias

• Issues with generalisability

What is volunteer bias?

Volunteer bias occurs when the participants who choose to take part in a study are systematically different from those who do not, making the sample unrepresentative.

Why may volunteer sampling have low generalisability?

Volunteer sampling can have issues with generalisability because the people who choose to take part are often not representative of the wider population. They tend to share certain characteristics (e.g., more motivated, confident), which creates volunteer bias.

What is Stratified sampling?

A sophisticated form of sampling in which the sample reflects the proportions of people in certain sub-grounds within the target/wider population

How is stratified sampling carried out?

To carry out stratified sampling, the researcher first identifies the different sub-grounds that make up the population. Then, the proportions needed for the sample to be representative are worked out, then, pps that make up each stratum are selected using random sampling

What are strengths of stratified sampling?

• avoids researcher bias Issues

• Representative sample

• Can be generalised

What are weakness of stratified sampling?

• stratification is not perfect- identified strata may not reflect all sub groups

• Complete representativeness is not possible