Sampling Techniques Flashcards
Random sampling
Definition and Example
- Every member of the population has an equal chance of being selected
- Names pulled out a hat
Random Sampling
Strengths and weaknesses
S- sample is likely to be very representative, researcher bias is not possible
W- the sample may still be unrepresentative, especially if it is small
Opportunity sampling
Definition and example
- obtaining people who are available at a certain time/place to take part
- e.g selecting student who happen to be walking passed the library at 12:30
Opportunity sampling
Strengths and weaknesses
S - a very fast way to gather participants. Less time, money and resources
W - the sample is drawn from a very narrow part of the target population
Volunteer sampling
Definition and examples
- p’s self select by responding to an ad placed in a strategic place
- e.g. people responding to an advert placed in a sports center
Volunteer sampling
Strengths and Weaknesses
S - requires minimum input, the p’s come to you. Ethical
W - volunteers are already motivated to engage, it attracts certain people
Systematic sampling
Definition and example
- every nth member of the target population is selected and placed in different conditions
- e.g list all 500 names, pick every 10th person, get a sample of 50
Systematic sampling
Strengths and weaknesses
S - p’s selected should, in theory, be representative and unbiased
W - the system doesn’t guarantee representativeness
Stratified sampling
Definition and example
- identify key stratum (layers), calculate correct proportions for each based on target group, samples then selected randomly
- e.g if 12% of the group are aged between 20-30, in a sample of 100 there should be 12 p’s aged between 20-30
Stratified sampling
Strengths and weaknesses
S - end up with an extremely representative sample
W - time consuming and difficult to execute
