Sampling, Chapter 6, 5

Question 1

What is population?

Answer 1

A group of people who are the focus of the researcher’s interest, from which a smaller sample is drawn

Question 2

What is a sample?

Answer 2

A group of people who take part in a research investigation. The sample is drawn from a target population and is presumed to be representative of that population, i.e. it stands ‘fairly’ for the population being studied

Question 3

What are sampling techniques?

Answer 3

The method used to select people from the population

Question 4

What is bias?

Answer 4

In the context of sampling, when certain groups are over- or under- represented within the sample selected.

For instance, there may be too many young people or too many people of one ethnic origin in a sample.

This limits the extent to which generalisations can be made to the target population

Question 5

What is generalisation?

Answer 5

The extent to which findings and conclusions from a particular investigation can be broadly applied to the population. This is possible if the sample of participants is representative of the target population

Question 6

What is a target population?

Answer 6

A subset of the general population

Question 7

What are examples of sample populations?

Answer 7

random sample, systematic sample stratified sample, opportunity sample volunteer sample

Question 8

What is a random sample?

Answer 8

A sophisticated form of sampling in which all members of the target population have an equal chance of being selected

Question 9

What is a systematic sample?

Answer 9

When every nth member of the target population is selected (e.g. every 3rd house on a street or every 5th pupil on a school register)

Question 10

What is a stratified sample?

Answer 10

A sophisticated form of sampling in which the composition of the sample reflects the proportions of people in certain subgroups (strata) within the target population or the wider population

Question 11

What is an opportunity sample?

Answer 11

Given that representative samples of the target population are so difficult to obtain, many researchers simply decide to select anyone who happens to be willing and available. The researcher simply takes the chance to ask whoever is around at the time of their study (e.g. in the street as in the case of market research)

Question 12

What is a volunteer sample?

Answer 12

This involves participants selecting themselves to be part of the sample

Question 13

What are the steps of random sampling?

Answer 13

1) obtain a complete list of all members of the target population
2) All of the names on the list are assigned a number
3) the actual sample is selected through the use of some lottery method ( a computer/ phone randomiser or picking numbers from a hat)

Question 14

What is produced in a systematic sample?

Answer 14

A sampling frame is produced which is a list of people in the target population organised into, for instance alphabetical order

Question 15

When is a sampling system nominated?

Answer 15

(every 3rd, 6th, or 8th person, etch)

Question 16

How may a systematic sample begin?

Answer 16

From a randomly determined start to reduce bias. The researcher then works through the sampling frame until the sample is complete

Question 17

How do you carry out a stratified sample?

Answer 17

The researcher first identifies the different strata that make up the population

Then, the proportions needed for the sample to be representative are worked out

Finally, the participants that make up each stratum are selected using random sampling

Question 18

What is an example of a stratified sample?

Answer 18

In Manchester, 40% of people support Man U, 40% support Manchester City, 15% support Bolton and 5% support Leeds.

In a stratified sample of 20 participants, there would be 8 United fans, 8 City fans, 3 Bolton and 1 solitary Leeds supporter

Each of these would be randomly selected from the larger group of fans of their team, e.g. Bolton fans selected Bolton supporters, if there are enough

Question 19

What is volunteer sample also referred to as?

Answer 19

Self-selection

Question 20

How does a researcher select a volunteer sample?

Answer 20

A researcher may place an advert in a newspaper or on a common room notice board. Alternatively, willing participants may simply raise their hand when the researcher asks

Question 21

How does a researcher select an opportunity sample?

Answer 21

The researcher simply takes the chance to ask whoever is around at the time of their study (e.g. in the street as in the case of market research)

Question 22

What are the strengths of a random sample?

Answer 22

Potentially unbiased so confounding or extraneous variables should be equally divided between the different groups, enhancing internal validity

Question 23

What are the limitations of a random sample?

Answer 23

Difficult and time-consuming to conduct. A complete list of the target population may be extremely difficult to obtain

You may end up with a sample that is unrepresentative- the laws of probability suggest that random sampling is likely to produce a more representative sample than, say, opportunity sampling

However selected participants many refuse to take part which means you end up with something more like a volunteer sample

Question 24

What are the limitations of a systematic sample?

Answer 24

Time-consuming and participants may refuse to take part, resulting in a volunteer sample

This sampling method is objective, once the system for selection has been established, the researcher has no influence over who is chosen (even more the case if the start is randomly selected)

Question 25

What are the strengths of a stratified sample?

Answer 25

Produces a representative sample because it is designed to accurately reflect the composition of the population. This means that generalisation of findings become possible

Question 26

What are the limitations of a stratified sample?

Answer 26

Stratification is not perfect. The identified strata can not reflect all the ways that people are different, so complete representation of the target population is not possible

Question 27

What are the strengths of an opportunity sample?

Answer 27

It is convenient. This method is much less costly in terms of time and money than say, random sampling because a list of members of the target population is not required and there is no need to divide the population into different strata as there is in stratified sampling

Question 28

What are the limitations of an opportunity sample?

Answer 28

They suffer from two forms of bias. First, the sample is unrepresentative of the target population as it is drawn from a very specific area such as one street in one town, so findings cannot be generalised to the target population

The researcher has complete control over the selection of participants and, for instance, may avoid people they do not like the look of (researcher bias)

Question 29

What are the strengths of a volunteer sample?

Answer 29

Collecting a volunteer sample is easy. It requires minimal input from the researcher (they come to you) and so is less time-consuming than other forms of sampling

The researcher ends up with participants who are more engaged, more so than someone who was stopped on the street

Question 30

What are the limitations of a volunteer sample?

Answer 30

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)