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 (ie 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

The majority of samples are biased in that certain groups may be over or under represented

Question 5

Opportunity Sample

How?

Answer 5

People who are simply most available (ie the ones who are nearest/easiest to obtain)

Ask people nearby

Question 6

One Strength of an Opportunity Sample

Answer 6

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

Question 7

One Limitation of an Opportunity Sample

Answer 7

• Inevitably biased. The sample is unrepresentative of the target population as it is drawn from a very specific area. This means that the findings cannot be generalised

Question 8

Volunteer Sample

How?

Answer 8

Participants select themselves (ie self-selecting)

Advertise

Question 9

One Strength of a Volunteer Sample

Answer 9

+ 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 10

One Limitation of a Volunteer Sample

Answer 10

• Likely to be a biased sample. Participants may share certain traits. Therefore, generalisation is limited due to volunteer bias

Question 11

Random Sample

How?

Answer 11

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

Lottery method. All members of the target population are given a number and placed in a hat or a tombola

Question 12

One Strength of a Random Sample

Answer 12

+ Potentially unbiased. The researcher has no influence over who is selected. Free from researcher bias

Question 13

One Limitation of a Random Sample

Answer 13

• Representation not guaranteed. Still possible that a random method may produce a biased sample. Limits ability to generalise

Question 14

Systematic Sample

How?

Answer 14

Participants are selected using a set pattern (sampling frame)

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

Question 15

One Strength of a Systematic Sample

Answer 15

+ Unbiased. The first item is usually selected at random. Therefore, an objective method

Question 16

One Limitation of a Systematic Sample

Answer 16

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

Question 17

Stratified Sample

How?

Answer 17

Frequency. Participants are selected according to their frequency in the target population

Subgroups (or strata) are identified (eg gender or age groups). The relative percentages of the subgroups in the population are reflected in the sample

Question 18

One Strength of a Stratified Sample

Answer 18

+ Representative method. The characteristics of the target population are represented. Therefore, generalisability is more likely than other methods

Question 19

One Limitation of a Stratified Sample

Answer 19

• Stratification is not perfect. Strata cannot reflect all the ways in which people are different. Therefore, complete representation is not possible