methods: sampling techniques

Question 1

what is the aim of sampling methods, and what is sampling bias?

Answer 1

• to ensure a representative sample of ppts
• sample should reflect the characteristics of the target population
• allows conclusions to be generalised to the whole population
• sampling bias:
• occurs when there is overrepresentation or underrepresentation of a particular type of ppt
• results in a sample that is not representative, which can distort findings and limit generalisability

Question 2

what is the target population, and how is a sample selected?

Answer 2

• the group of people the study is about
• findings are intended to be applied to this group
• eg study on attitudes about the NHS at a local hospital would have people at the hospital as the target population
• sample:
• subset of the target population
• selected using a sampling technique to take part in the study

Question 3

what is opportunity sampling in psychological research?

Answer 3

• involves selecting participants who are available at the time the study is conducted
• ppts must fit the criteria the researcher is looking for
• commonly used by psychology students due to ease and convenience

Question 4

what is random sampling, and how is it carried out?

Answer 4

• every member of the target population has an equal chance of being selected
• requires identifying everyone in the population
• ppts are then selected using a random method (eg random number generator or lottery system)
• ensures unbiased selection

Question 5

what is stratified sampling and how does it work?

Answer 5

• involves classifying the population into categories (strata)
• a sample is selected that includes participants from each category
• proportions of each category in the sample match their proportions in the target population
• ensures a representative sample

Question 6

what is self-selected (volunteer) sampling?

Answer 6

• ppts become part of a study because they volunteer
• they may respond to a request or advertisement
• common in psychological research where participants opt in to take part

Question 7

strengths of opportunity sampling

Answer 7

• more ethical:
• researcher can judge if a ppt may be upset by the study or too busy to take part
• provides more info about ppts before selection
• quick and efficient:
• researcher has more control over who is asked
• easy access to ppts makes the process faster and more practical

Question 8

weaknesses of opportunity sampling

Answer 8

• higher risk of bias:
• researchers have more control over selection, which can lead to selection bias
• may favour certain people:
• likely to choose people who are easily accessible (eg friends or acquaintances)
• may choose ppts who are similar to themselves, such as in age or appearance
• increases the chance of a biased sample, reducing representativeness and generalisability
• those who are available and willing to take part are, in effect, self-selected
• this can introduce further bias, as such individuals may not reflect the wider population

Question 9

strengths of random sampling

Answer 9

• everyone in the target population has an equal chance of being selected
• this means the sample is likely to be representative of the target population
• it’s clear to everyone how the sample was chosen, and each step can be explained and understood
• studies using random sampling are seen as more scientific, and their results and conclusions are more widely recognised
• any possible bias can be worked out mathematically and taken into account

Question 10

weaknesses of random sampling

Answer 10

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Question 11

weaknesses of random sampling

Answer 11

• it’s hard to ensure everyone in the target population is available to take part, which can cause bias
• issues like the data protection act 1988 can make it difficult to obtain ppt details
• random sampling can lead to bias if certain groups aren’t selected
• eg, it may not select female soldiers in a study on obedience in male and female soldiers

Question 12

strengths of stratified sampling

Answer 12

• each group is bound to be represented, allowing for conclusions about differences between groups
• it’s an efficient way to ensure representation from each group
• it limits the number of ppts needed to obtain representation from each group

Question 13

weaknesses of stratified sampling

Answer 13

• it’s hard to determine how many individuals to choose from each group to ensure the findings are generalisable
• with small groups, it’s harder to determine an appropriate size
• the groups defined by the study may not represent the important groups, leading to the exclusion of some ppts
• this can result in a sample that’s not representative of the population

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Question 14

strengths of volunteer sampling

Answer 14

• more ethical as ppts come to researcher, rather than being sought out by the researcher
• volunteers are interested and less likely to give biased info or go against researcher’s instructions. while there might be demand characteristics, having willing ppts is generally an advantage

Question 15

weaknesses of volunteer sampling

Answer 15

• it can take a long time to gather enough ppts since the researcher must wait for volunteers to apply
• ppts who select themselves may be similar in some way, leading to a sample that’s not representative of the target population