Sampling Methods

Question 1

Samples selected without bias from a list of the entire target population

Answer 1

Random
Stratified
Systematic

Question 2

Samples selected with the potential of bias

Answer 2

Opportunity and volunteer sampling

Question 3

Random Sampling

Answer 3

A sample generated by identifying a lost of the target population and randomly selecting participants from this list (in an unbiased way)
The names of the entire target population can be put into a hat and drawn at random; alternatively, names could be randomly generated using a computer database.
Therefore, each member of the target population has an equal chance of being selected.

Question 4

Random Sampling Strength HPV

Answer 4

Unlike opportunity Sampling, where the researcher chooses the sample based on who is available at the time of the study, a strength is that it can often generate a sample with high population validity,
Which is when the results can be successfully generalised to the target population, increasing the external validity of research.
As each member of the target population has an equal chance of being selected, the sample is likely to be highly representative.

Question 5

Random Sampling Strength LEB

Answer 5

Unlike opportunity sampling, where the researcher chooses the sample based on who is available at the time of the study, a strength us that it has low experimenter bias,
Which is when the experimenter cannot show unintentional bias in the selection of the participants, increasing the internal validity of research
This is because the researcher doesn’t actively choose individuals as participants are selected in an unbiased manner

Question 6

Random Sampling Limitation LPV

Answer 6

A limitation is that it may not always generate a sample with high population validity
Which is extent to which results can be successfully generalised to the target population
Although the selection of participants is unbiased, the actual sample may be biased in some way if only one type of person is selected.
For example, by chance only female participants may be selected from a group of males and females, meaning the sample may not be representative of the population.

Question 7

Random Sampling limitation I

Answer 7

It is impractical,
As the full list of the target population may be difficult or impossible to obtain
For example, it may be difficult or impossible to define a complete list of all schizophrenics, meaning the sample drawn may be biased and this method cannot be used to study behaviour where no list of the target population exists

Question 8

Stratified Sampling

Answer 8

A sample generated by identifying a list of the entire target population as well as the characteristics which are important to the research (e.g. gender) before randomly selecting a ratio that reflects these groups (or strata)
If the target population is 40%female and 60% male, participants are drawn randomly until they reach this ratio, so the sample is representative of the structure of the target population

Question 9

Stratified Sampling Strength HPV

Answer 9

Unlike opportunity sampling, where only those people who are available at the time of the study can be selected, a strength is that it can often generate a sample with high population validity
Which is when the results can be successfully generalised to the target population, increasing the external validity of research
This is because an effort has been made to ensure the sample reflects the make-up of the target population, meaning the sample is likely to be highly representative

Question 10

Stratified Sampling Strength LEB

Answer 10

Unlike opportunity sampling, where only those people who are availableat the time of studycan be selected, a strength of stratified sampling is that it has low experimenter bias,
Which is when the experimenter cannot show unintentional bias in the selection of participants, increasing the internal validity of research.
Although the experimenter identifies strata in the target population, he does not actively choose individuals, and participants are still selected in an unbiased manner.

Question 11

Stratified Sampling limitation LPV

Answer 11

A limitation of stratified sampling is that it may not always generate a sample with high population validity,
Which is to the extent at which results can be successfully generalised to the target population.
Although the selection of participants reflects the known strata of the target population, the actual sample may still be biased if (by chance) only participants with an unknown characteristic are selected.

Question 12

Stratified Sampling limitation IDA

Answer 12

A limitation of stratified sampling is that it is difficult and time consuming to achieve.
This is because it is challenging to fully identify the characteristics of the target population that are important to research.
For example, whilst some characteristics (like gender) are easy to identify, others (like IQ) are hidden and difficult to define and this method cannot be used to study behaviour where no list of the target population exists.

Question 13

Systematic sampling

Answer 13

A sample generated by identifying a list of the entire target population before specifically selecting every nth participant.
For example, if there are 100 people in the target population and a sample of 20 is required, psychologists would select every 5th person from the list. (100÷20=5)

Question 14

Systematic sampling strength HPV

Answer 14

Unlike opportunity sampling, where only those people who are available at the time of study can be selected, a strength of systematic sampling is that it can often generate a sample with high population validity.
Which is when the results can be successfully generalised to the target population, increasing the external validity of the research.
This is because the sample will show an unbiased representation of the target population, meaning the sample is likely to be highly representative.

Question 15

Systematic sampling strength LEB

Answer 15

Unlike opportunity sampling, where only those people who are available at the time of study can be selected, a strength of systematic sampling is that it provides low experimenter bias.
Which is when the experimenter cannot show unintentional bias in the selection of participants, increasing the internal validity of research.
Although the experimenter identifies the nth person from the target population, he does not actively choose individuals, and participants are still selected in an unbiased manner.

Question 16

Systematic sampling limitation LPV

Answer 16

A limitation of systematic sampling is that it may not always generate a sample with high population validity,
Which is when the extent to which results can be successfully generalised to the target population.
Although the selection of participants is unbiased, the actual sample may be biased in some way if (by chance) only one type of person is selected.
If every nth person happens to share some characteristic (e.g. they all happen to be young and female), the sample may not be representative of the population.

Question 17

Systematic sampling limitation I

Answer 17

A limitation of systematic sampling is that it is impractical
As it still requires psychologists to devise a full list of the target population, which may be difficult or impossible to obtain.
For example it may be difficult or impossible to define a complete list of all schizophrenics, meaning the sample drawn may be biased and this method cannot be used to study behaviour where no list of the target population exists.

Question 18

Opportunity sampling

Answer 18

A sample generated when participants take part in research based on their availability at the time of the study, often by agreeing (having first been approached by the experimenter).
Here, the researcher asks available people if they are willing to take part, for example stopping people in a high street. Those who agree become his sample.

Question 19

Opportunity sampling strength P

Answer 19

A strength of opportunity sampling is that it is practical,
As it is a straightforward method that requires little time or preparation to perform.
This is because the researcher simply selects participants based on their availability at the time of the research.
Therfore, the method is less expensive than other methods, such as random sampling, which require significant preliminary work to be carried out. Indeed, Sears (1986) found that 75% of university research uses undergraduates because of their free availability.

Question 20

Opportunity sampling strength E

Answer 20

A strength of opportunity sampling is that it meets the ethical guidelines of gaining general consent from participants,
Which is when they are made aware of the experiment’s aims, procedures and anticipated findings before agreeing to take part in a study.
This is because details of the study will be described by the experimenter before they agree to take part in the experiment, allowing participants to make a more informed decision about whether to take part.

Question 21

Opportunity sampling limitation LPV

Answer 21

A limitation of opportunity sampling is that it has low population validity,
Which is when the findings of research cannot be generalised to the target population, decreasing the external validity of the study.
This is because opportunity samples are generated when participants agree to take part, having been approached by the experimenter, meaning this sampling method may miss other groups of people who are unwilling or unable to take part in research.

Question 22

Opportunity sampling limitations HEB

Answer 22

Unlike random sampling, where the selection of participants is unbiased because neither the researcher nor the participants chose who is selected, a limitation of opportunity sampling is that it has high experimenter bias,
Which is when the experimenter shows unintentional bias in the selection of participants, lowering the internal validity of research.
This is because the researcher directly asks people if they want to participate in the research, meaning he may show unintentional bias in his selection, by only asking certain kinds of people (e.g. those who look helpful)

Question 23

Volunteer sampling

Answer 23

A sample generated when participants self-select or volunteer to take part in research, normally in response to an advert.
A psychologist may place an advert online or in a newspaper and select those who respond.

Question 24

Volunteer sampling strength P

Answer 24

A strength of volunteer sampling is that it is practical,
As it is a straightforward method that requires little time or preparation to perform (other than producing an advert).
This is because the sample is constructed from self-selecting participants, based on their response to an advert.
Therfore, the method is less expensive than other methods, such as random sampling, which require significant preliminary work to be carried out.

Question 25

Volunteer sampling strength E

Answer 25

A strength of volunteer sampling is that it meets the ethical guidelines of gaining general consent from participants,
Which is when they are made aware of the experiment’s aims, procedures and anticipated findings before agreeing to take part in a study.
This is because details of the study will be placed on the advert, allowing participants to make a more informed decision about whether to take part.

Question 26

Volunteer sampling limitation LPV

Answer 26

A limitation of volunteer sampling is that it has low population validity,
Which is when the findings of research cannot be generalised to the target population, decreasing the external validity of the study.
This is because volunteer samples are generated when participants choose to take part after responding to an advert, meaning this sampling method may miss other groups of people who are unwilling or unable to take part in the research.