Sampling

Question 1

What is meant by a ‘population’?

Answer 1

• A group of people who are the focus of the researchers interest, from which a smaller sample is drawn
• The sample that is drawn will be representitative of the target population

Question 2

What is random sampling?

Answer 2

• Where all members of the target population have an equal chance of being selected
• To select a random sample you have to obtain a complete list of all members of target population
• All of the names on the list will be assigned a number
• Finally, the actual sample is selected through use of some lottery method (a comupture randomiser/picking numbers from a hat)

Question 2

What is meany by a ‘sample’?

Answer 2

• A group of people who take part in a research investigation
• The sample is drawn from a (target) population & is presumed to be representitative of that population

Question 3

What are the strengths of random sampling?

Answer 3

• A random sample is potentially unbiased- confounding & extraenuous variables should be equally divided between the different groups,
• Enhancning internal validity

Question 4

What are the limitations of random sampling?

Answer 4

• It is difficult & time consuming to conduc- a complete list of the target population may be extremely difficult to obtain
• Possibility you may still end up with a sample that it unrepresentitative
• Selected ppts may refuse to take part (meaning you end up with something more like a volunteer sample)

The last issue applies to all of sampling methods

Question 5

What is systematic sampling?

Answer 5

• When every nth member of the target population is selected
• A sampling frame is produced which a list of people in the target population organised into
• A sampling system is nominated
• May begin from a randomly determined start to reduce bias
• The researcher then works through the sampling frame until the sample is complete

Question 6

What are the strengths and limitations of systematic sampling?

Answer 6

Strengths:
- Sampling methods are objective - once system for selection has been established the researcher has no influence over who is chosen

Limitations:
- As with random sampling, this method is time consuming& in the end ppts may refuse to take part, resulting in a volunteer sampling

Question 7

What is stratified sampling?

Answer 7

• Where the composition of the sample reflects the proportions of people in certain subgroups (strata) within the target or wider population

Question 8

How would you carry out stratified sampling?

Answer 8

• The researcher first identifies the different strata that make up the population
• Then the proportions needed for the sample to be representitative are worked out
• Finally the participants that make up each stratum are selected using random sampling

Question 9

What are the strengths and weaknesses of stratified sampling?

Answer 9

Strengths:
- This method produces a representitative sample because it is designed to accurately reflect the composition of the population
- This means that generalisation of findings becomes possible

Weaknesses:
- Stratification is not perfect- the identified strata cannot reflect all the ways that people are different, so complete representation of the target population is not possible

Question 10

What is opportunity sampling?

Answer 10

• Where the researcher simply takes the chance to ask whoever is around at the time of their study
• e.g. the street

Question 11

What are the strengths and weaknesses of opportunity sampling?

Answer 11

Strengths:
- It is convenient & is less costly in terms of time & money than e.g. random sampling

Weaknesses:
- Opportunity sampling sufferes from two forms of bias:
- Sample is unrepresentitative of target population as it is drawn from a very specific area so findings cannot be generalised
- The researcher has full control over selection of ppts & for e.g. may avoid people they don’t like the look of (researcher bias)

Question 12

What is volunteer sampling?

Answer 12

• Involves ppts selecting themselves to be part of a sample/ research
• To select a volunteer sample, a researcher may place an advert in a newspaper or on a common room notice board.
• Alternitavely willing ppts may simply raise their hand when researcher asks

Question 13

What are the strengths and weaknesses for volunteer sampling?

Answer 13

Strengths:
- Collecting a volunteer sample is easy- it requires minimal input from the researcher & so is less time consuming than other forms of sampling
- The researcher ends up with ppts who are more engaged, more so than someone who was stopped in the street

Weaknesses:
- Volunteer bias is a problem- asking for volunteers may attract a certain ‘profile’ of person, that is one who is curious and more likely to try to please the researcher
- (which might then affect how far findings can be generalised)