4.2.3 - 4 Sampling Methods

Question 1

at the beginning of the research process, what must the researcher identify?

Answer 1

the target population

Question 2

give examples of target populations a researcher might identify

Answer 2

• women aged 35–50 years old who have survived breast cancer
• people who live in large cities in the uk
• university students who are taking stem subjects

Question 3

from where is the sample used in psychological research taken?

Answer 3

the sample is taken from a target population

Question 4

how is a sample often taken in psychological research?

Answer 4

often a sample is taken from a population that is more generalised than a target population

Question 5

give an example of a researcher needing a distinct target population

Answer 5

a researcher who wishes to investigate the effects of being a single teen parent will require their sample to be drawn from that specific population

Question 6

what is the single teen parent example an illustration of?

Answer 6

a distinct target population

Question 7

when running an experiment on the duration of short-term memory (stm), what type of target population is needed?

Answer 7

generally, anyone aged 18 to 60 years old would suffice, so a distinct target population is not required

Question 8

what does the researcher do after drawing a sample from the population?

Answer 8

the researcher generalises the findings across the target population

Question 9

what is random sampling?

Answer 9

random sampling involves obtaining a sample from a population in a way that has the least bias of all sampling methods

Question 10

what is true about the chance of being selected in random sampling?

Answer 10

every member of the population has an equal chance of being selected

Question 11

how can a random sample be achieved manually?

Answer 11

• put all names of the population in a hat
• draw out one name at a time until the required sample size is reached (e.g., 50 participants)

Question 12

how can a random sample be achieved for large samples?

Answer 12

employ a computer name-generator software (useful for large samples, e.g., 2,000 participants)

Question 13

what are the strengths of random sampling?

Answer 13

• eliminates researcher bias as the researcher has no control over selection
• results should be fairly representative
• findings can be generalised to the target population

Question 14

what are the limitations of random sampling?

Answer 14

• can be time-consuming and impractical
• may not be possible to access all information on the target population
• not everyone selected may want to take part
• can result in a non-representative sample (e.g., all-male sample)

Question 15

what is systematic sampling?

Answer 15

systematic sampling involves selecting every nth person from a list to make a sample

Question 16

give an example of systematic sampling

Answer 16

selecting every 10th, 100th, or 1000th person on a register/database/roll depending on the population and sample size required

Question 17

how is the sampling interval in systematic sampling calculated?

Answer 17

by dividing the population size by the required sample size

Question 18

give an example of calculating a sampling interval

Answer 18

• population = 100,000
• required sample = 2,500
• 100,000 ÷ 2,500 = 40
• every 40th person on the list is selected for the sample

Question 19

what are the strengths of systematic sampling?

Answer 19

• unbiased, as the researcher has no control over list placement
• more representative than some other methods
• representative samples are more easily generalised
• quick, easy, and cost-effective → popular with researchers and funders

Question 20

what are the limitations of systematic sampling?

Answer 20

• not completely free from bias due to hidden periodic traits (e.g., if every 10th person is a 19-year-old female nurse)
• researcher must know the population size to calculate sample interval
• without this, generalisability may be limited

Question 21

what does stratified sampling aim to generate?

Answer 21

a small-scale reproduction of the target population

Question 22

how is stratified sampling carried out?

Answer 22

• divide the target population into key categories relevant to the research (e.g., age, gender, education level, ethnicity, profession)
• sample within each category in proportion to its representation in the total population

Question 23

give an example of proportional representation in stratified sampling

Answer 23

if 18% of the total population are males aged 30–40, the sample will also include 18% males aged 30–40

Question 24

what are the strengths of stratified sampling?

Answer 24

• representative of the target population based on exact proportions
• allows for easy generalisation to the wider population
• researcher controls chosen categories to match the research aim

Question 25

what are the limitations of stratified sampling?

Answer 25

- difficult to classify every member of the population into subgroups - time-consuming to gather sample population data - not always possible to access all information on the target population

Question 26

what is opportunity sampling?

Answer 26

opportunity sampling involves the researcher obtaining their sample from those who are present and available at the time and willing to take part

Question 27

give examples of opportunity sampling

Answer 27

- people shopping in a supermarket at 11am - university students at one of the researcher’s lectures - young parents at a baby yoga group

Question 28

what is another name for opportunity sampling?

Answer 28

convenience sampling

Question 29

what are the strengths of opportunity sampling?

Answer 29

- quick and easy to obtain participants - convenience allows smooth running of research - participants who willingly agree are less likely to harm study validity

Question 30

what are the limitations of opportunity sampling?

Answer 30

- not possible to generalise as the sample only represents those available and willing at that time - researcher may show unconscious bias when selecting participants, e.g.: -> approaching people they feel comfortable with -> choosing those who seem interested -> avoiding certain social groups (e.g., males aged 18–25)

Question 31

what is volunteer sampling?

Answer 31

volunteer sampling involves people actively selecting themselves to participate in a study — they volunteer to take part

Question 32

what is another name for volunteer sampling?

Answer 32

self-selecting sampling

Question 33

how might a researcher find participants for a volunteer sample?

Answer 33

- put up posters/flyers around a university campus - post adverts on social media - run an advert in a print newspaper

Question 34

what information might a volunteer advert include?

Answer 34

when and where the study takes place and how to participate

Question 35

what might a volunteer sampling advert specifically ask for?

Answer 35

people with certain characteristics, e.g.: - first-time parents - people with adhd - bilingual people

Question 36

what are the strengths of volunteer sampling?

Answer 36

- quick, easy, and cost-effective - one of the most used (and probably most popular) sampling methods - participants are willing and enthusiastic - volunteers are less likely to jeopardise the study

Question 37

what are the limitations of volunteer sampling?

Answer 37

- prone to volunteer bias -> results not easily generalisable (volunteers may share traits like sociability or eagerness) - tendency to please the researcher may cause demand characteristics → lowers validity