research methods: Sampling

Question 1

What does population mean?

Answer 1

The large group of individuals that a particular researcher is interested in studying

Question 2

What is a target population?

Answer 2

Every member of the group that the investigator plans to study

Question 3

Why do researchers use samples from the target population?

Answer 3

As it is impossible for the researcher to choose everyone in the population, a small amount of people are used, assumed to be representative of the target population

Question 4

What does sampling allow?

Answer 4

Allows generalising of findings to become possible

Question 5

What are the different types of sampling?

Answer 5

• random sampling
• systematic sampling
• stratified sampling
• opportunity sampling
• volunteer sampling

Question 6

What is random sampling?

Answer 6

When each member of the target population has an equal chance of being in the experiment’s sample

Question 7

Outline the steps of random sampling:

Answer 7

1) The researcher obtains a complete list of the entire target population
2) All the names on the list are assigned a number
3) The sample is selected through the use of some lottery method such as a computer

Question 8

What are the strengths of random sampling?

Answer 8

• a random sample avoids researcher bias as the researcher cannot choose the pps they want to form the sample
• this avoids the possibility that the researcher picks participants they feel are likely to give a preferred result
• confounding/extraneous variables are equally divided between the different groups, enhancing the validity

Question 9

What are the limitations of random sampling?

Answer 9

• difficult and time-consuming to get a full list of a large target population
• you may end up with a sample that is unrepresentative
• for example, too few members of one gender or with no members of a minority group

Question 10

What is systematic sampling?

Answer 10

When every nth member of the target population is selected to form the sample

Question 11

Outline the steps of conducting systematic sampling?

Answer 11

1) The researcher needs a full list of the entire target population
2) The researcher reads down the list selecting every Nth participant to form the sample
3) the process continues until the sample required is chosen

Question 12

What are the advantages of systematic sampling?

Answer 12

• the sampling is objective so free from researcher bias as the researcher cannot choose the participants they want in their sample
• if there is an existing list of a target population, it can be a quick method of selecting a sample

Question 13

What are the limitations of systematic sampling?

Answer 13

• Method is time-consuming if the target population is very large so getting a full list could be difficult
• by chance this method could result in an unrepresentative sample

Question 14

What is stratified sampling?

Answer 14

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

Question 15

Outline the steps of conducting stratified sampling:

Answer 15

1) Strata (subgroups) are identified along with their proportion in the target population
2) Random sampling is then used to select the number of pps required from within each stratum

Question 16

What are the advantages of stratified sampling?

Answer 16

• the sample is representative of the larger population, meaning the results found within the sample should be generalisable to the target population
• as the participants are randomly chosen from within each stratum this avoids researcher bias

Question 17

What are the limitations of stratified sampling?

Answer 17

• Not every possible characteristic can be included in a stratified sample, and as the researcher decides which strata are important, this may result in bias
• time-consuming to establish strata and then randomly select from each stratum

Question 18

What is opportunity sampling?

Answer 18

The researcher directly asks available members of the target population to take part in the research
- likely to be individuals the researcher has easy access to and is familiar with

Question 19

Outline the steps of conducting opportunity sampling:

Answer 19

1) Researchers directly asks any members from within the target population to take part in the research
2) Any individuals who agree to take part are added to the sample until the number of participants required is met

Question 20

What are the advantages of opportunity sampling?

Answer 20

• This is the fastest way to get a sample for psychological research
• reduces the time it takes to conduct research (easy to conduct)
• likely reduces the cost involved compared to more complex sampling methods

Question 21

What are the limitations of opportunity sampling?

Answer 21

• Suffers from two forms of bias
• First, opportunity samples are unlikely to be representative as the participants chosen are the type of people the researcher has easy access to and drawn from a very specific area
• Secondly, the researcher has complete control over the selection of participants and may select those they feel are likely to produce a preferred result, resulting in researcher bias

Question 22

What is volunteer sampling?

Answer 22

Participants offer to take part after finding out about the research, likely after seeing an advert in a newspaper or online

Question 23

What are the advantages of volunteer sampling?

Answer 23

• collecting a volunteer sample is easy as participants are putting themselves forward rather than having to be found individually and contacted directly
• advertising for participants can reach a very large number of potential participants, especially if the newspaper or website is widely read
• researcher ends up with participants who are more engaged

Question 24

What are the limitations of volunteer sampling?

Answer 24

• The sample may not be generalisable to the target population because of volunteer bias
• the types of people who volunteer to take part likely have different characteristics to the target population
• likely to be friendlier and have more free time available
• attracts a certain ‘profile’ of person