Sampling

Question 1

Population

Answer 1

The large group of people that a researcher is interested in studying.

Question 2

Sample

Answer 2

It is usually not possible to include all members of the population in the study, so a smaller group is selected - the sample.

Question 3

Generalisation

Answer 3

The sample that is drawn should be representative of the population so generalisations can be made.

Question 4

Bias

Answer 4

Most samples are biased in that all certain groups may be over - or under - represented.

Question 5

Random sample

Answer 5

Every person in the target population has an equal chance of being selected.

Question 6

How is a random sample technique used?

Answer 6

Lottery method. All members of the target population are given a number and placed in a hat or computer/phone randomiser used.

Question 7

What is a strength of random sampling?

Answer 7

Potentially unbiased.
This means CVs/EVs are controlled.
Enhances internal validity.

Question 8

What is a limitation of random sampling?

Answer 8

Time consuming and may not work.
Complete list of population is hard to get.
Also some participants may refuse to take part.

Question 9

Systematic sample

Answer 9

Participants are selected using a set pattern/system (sampling frame).

Question 10

How is a systematic sample technique used?

Answer 10

Every nth person is selected from a list of the target population.

Question 11

What is a strength of systematic sampling?

Answer 11

Unbiased.
The first item is usually selected at random.
Objective method.

Question 12

What is a limitation of systematic sampling?

Answer 12

Time and effort.
A complete list of the population is required.
May as well use random sampling.

Question 13

Stratified sample

Answer 13

Sample reflects proportions of people in certain subgroups (strata) within a population.

Question 14

How is a stratified sample technique used?

Answer 14

Subgroups (strata) are identified e.g. gender or age. The relative percentages of the subgroup in the population are reflected in the sample.

Question 15

What is a strength of stratified sampling?

Answer 15

Representative method.
The characteristics of the target population are represented.
Generalisability more likely than other methods.

Question 16

What is a limitation of stratified sampling?

Answer 16

Stratification is not perfect.
Strata cannot reflect all ways in which people are different.
Complete representation is not possible.

Question 17

Opportunity sample

Answer 17

People who are simply most available i.e. easiest/nearest to obtain.

Question 18

How is an opportunity sample technique used?

Answer 18

Ask people nearby.

Question 19

What is a strength of opportunity sampling?

Answer 19

Quick method.
Opportunity sampling is convenient because you just make use of the people who are closest.
This makes it cheaper and one of the most popular sampling methods.

Question 20

What is a limitation of opportunity sampling?

Answer 20

Inevitably biased.
The sample is unrepresentative of the target population as it is drawn from a very specific area, such as one street in town.
This means that findings cannot be generalised.

Question 21

Volunteer sample

Answer 21

In a volunteer sample, participants select themselves.

Question 22

How is a volunteer sample used?

Answer 22

Advertise.

Question 23

What is a strength of volunteer sampling?

Answer 23

Participants are willing.
Participants have selected themselves and know how much time and effort is involved.
Likely to engage more than people stopped in the street.

Question 24

What is a limitation of volunteer sampling?

Answer 24

Volunteer bias.
Participants may share certain traits.
Respond to cues and generalisation limited.