Sampling Flashcards
Population
The large group of people that a researcher is interested in studying, for example college students from the North West.
Sample
It is usually not possible to include all members of the population in the study, so a smaller group is selected- the sample.
Generalisation
The sample that is drawn should be representative of the population so generalisations can be made.
Bias
Most samples are biased in that certain groups may be over- or under- represented.
Random Sample
-Every person in the target population has an equal chance of being selected.
-Lottery methods- all members of the target population are given a number and placed in a hat or computer/phone randomiser used.
A03 (+)
P- Potentially unbiased
E- This means CV’s/EV’s are controlled
E- Enhances internal validity
A03 (-)
P- Time consuming and may not work
E- Complete list of population is hard to get
E- Also some participants may refuse to take part
Systematic Sampling
-Participants are selected using a set ‘pattern’
-Every nth person is selected from a list of the target population
A03 (+)
P- Unbiased
E- The first item is usually selected at random
E- Objective Method
A03 (-)
P- Time and effort
E- A complete list of the population is required
E- May as well use random sampling
Stratified Sample
-Sample reflects proportions of people in certain subgroups within a population.
-Subgroups are identified. The relative percentages of the subgroups in the population are reflected in the sample.
A03 (+)
P- Representative Method
E- The characteristics of the target population are represented
E- Generalisability more likely than other methods
A03 (-)
P- Stratification is not perfect
E- Strata cannot reflect all the ways in which people are different.
E- Complete representation is not possible
Opportunity Sample
-People who are simply most available
-Ask people nearby
A03 (+)
P- Quick method
E- Opportunity sampling is convenient because you just make use of the people who are closest.
E- This makes it cheaper and one of the most popular sampling methods
A03 (-)
P- Inevitably biased
E- The sample is unrepresentative of the target population as it is drawn from a very specific area, such as one street in one town
E- This means that the findings cannot be generalised
Volunteer Sample
-In a volunteer sample, participants select themselves
-Advertise. For example, place an advert in a newspaper or ask people to put hands up to volunteer
A03 (+)
P- Participants are willing
E- Participants have selected themselves and know how much time and effort is involved
E- Likely to engage more than people stopped in the street
A03 (-)
P- Volunteer bias
E- Participants may share certain traits
E- Respond to cues and generalisation limited
