7.2: Sampling Flashcards
Sampling
Sampling is the selection of participants to represent a wider population
Reducing it each time:
Population —> what —> what?
Population —> Target population —> Sample
In psychological research studies, what is the population?
In psychological research studies, the population is a large group of people that the researcher is interested in studying
In psychological research studies, the population is a large group of people that the researcher is interested in studying.
What is it usually?
The population is usually a very specific group of people
In psychological research studies, the population is a large group of people that the researcher is interested in studying.
The population is usually a very specific group of people.
Example
For example, children with autumn under 6 years old
In psychological research studies, the population is a large group of people that the researcher is interested in studying.
The population is usually a very specific group of people.
For example, children with autumn under 6 years old.
What is this called?
This is called the target population
In psychological research studies, the population is a large group of people that the researcher is interested in studying.
The population is usually a very specific group of people.
For example, children with autumn under 6 years old.
This is called the target population.
Within the target population, what will the researcher do?
Within the target population, the researcher will take an even smaller group of people called the sample
In psychological research studies, the population is a large group of people that the researcher is interested in studying.
The population is usually a very specific group of people.
For example, children with autumn under 6 years old.
This is called the target population.
Within the target population, the researcher will take an even smaller group of people called the sample.
Example
For example, 20 children with autumn under 6 years old
When is a group of participants representative?
A group of participants is representative if selected from a larger population so that it closely matches the characteristics of the population as a whole
A group of participants is representative if selected from a larger population so that it closely matches the characteristics of the population as a whole.
The sample is a fairly what reflection of the population from which the sample is drawn?
The sample is a fairly accurate reflection of the population from which the sample is drawn
Generalisation
Generalisation is the extent to which the findings from a study can be broadly applied to the population
Generalisation is the extent to which the findings from a study can be broadly applied to the population, so if the sample is representative, what?
Generalisation is the extent to which the findings from a study can be broadly applied to the population, so if the sample is representative, the more likely it is that we can achieve this
Bias
Bias is when certain groups are over or under represented within the sample
Bias is when certain groups are over or under represented within the sample.
Example
For example, too many women, men, ect
Bias is when certain groups are over or under represented within the sample.
For example, too many women, men, ect.
What does this do?
This limits the extent to which generalisations can made to the population
Why do researchers use sampling?
Researchers use sampling, because they don’t generally have the means to test whole populations
Samples are selected using sampling techniques that aim to do what?
Samples are selected using sampling techniques that aim to produce a representative sample
Random sampling
Random sampling is where each member of a population has an equal chance of being selected
Random sampling is where each member of a population has an equal chance of being selected.
What is one way to achieve this?
One way to achieve this is the lottery method
Random sampling is where each member of a population has an equal chance of being selected.
One way to achieve this is the lottery method - what happens?
One way to achieve this is the lottery method - all the members of the target population are:
- Given a number
- Placed in a hat or tombola
Random sampling is where each member of a population has an equal chance of being selected.
One way to achieve this is the lottery method - all the members of the target population are given a number and placed in a hat or tombola.
What are also used to generate random lists?
Computer programs are also used to generate random lists
Random sampling is where each member of a population has an equal chance of being selected.
One way to achieve this is the lottery method - all the members of the target population are given a number and placed in a hat or tombola.
Computer programs are also used to generate random lists.
What does this result in?
This results in a sample selected in an unbiased fashion
Opportunity sampling
Opportunity sampling involves selecting participants who are:
- Available
- Willing to take part
Opportunity sampling involves selecting participants who are available and willing to take part.
Example
For example, asking people in the street who are passing
Opportunity sampling involves selecting participants who are available and willing to take part.
For example, asking people in the street who are passing.
What did Sears (1986) find?
Sears (1986) found that 75% of university research studies use undergraduates as participants, simply for the sake of convenience
What is volunteer sampling also known as?
Volunteer sampling is also known as self-selected
Volunteer (self-selected) sampling
Volunteer (self-selected) sampling involves people volunteering to participate
Volunteer (self-selected) sampling involves people volunteering to participate.
They select themselves as participants, often by doing what?
They select themselves as participants, often by replying to adverts
Systematic sampling
Systematic sampling is when participants are selected using a set pattern, as every nth person is taken from a list to create a sample
Systematic sampling is when participants are selected using a set pattern, as every nth person is taken from a list to create a sample.
What does this involve?
This involves:
- Calculating the size of the population
- Then assessing what size the sample needs to be to work out what the sampling interval is
Systematic sampling is when participants are selected using a set pattern, as every nth person is taken from a list to create a sample.
This involves calculating the size of the population and then assessing what size the sample needs to be to work out what the sampling interval is.
Example
For example, if a company has:
1. A workforce of 1,000 employees
2. A sample of 20 participants is required
,then 1,000 ÷ 20 = 50, so take every 50th name from the list of employees to form the sample
Stratified sampling
Stratified sampling is when participants are selected according to their frequency in the target population
Stratified sampling is when participants are selected according to their frequency in the target population.
What is a stratified sample?
A stratified sample is a small-scale reproduction of a population
Stratified sampling is when participants are selected according to their frequency in the target population.
A stratified sample is a small-scale reproduction of a population.
What does it involve?
It involves:
- Dividing a population into characteristics important for the research, for example by age, social class, ect
- Then the population is randomly sampled within each stratum (category)
Stratified sampling is when participants are selected according to their frequency in the target population.
A stratified sample is a small-scale reproduction of a population.
It involves dividing a population into characteristics important for the research, for example by age, social class, ect and then the population is randomly sampled within each stratum (category).
If 12% of the population is between 20 and 30 years old, then what?
If 12% of the population is between 20 and 30 years old, then 12% of the sample is randomly selected from that age sector
