Sampling Flashcards
Population
The large group of people that a researcher is interested in studying.
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 all certain groups may be over - or under - represented.
Random sample
Every person in the target population has an equal chance of being selected.
How is a random sample technique used?
Lottery method. All members of the target population are given a number and placed in a hat or computer/phone randomiser used.
What is a strength of random sampling?
Potentially unbiased.
This means CVs/EVs are controlled.
Enhances internal validity.
What is a limitation of random sampling?
Time consuming and may not work.
Complete list of population is hard to get.
Also some participants may refuse to take part.
Systematic sample
Participants are selected using a set pattern/system (sampling frame).
How is a systematic sample technique used?
Every nth person is selected from a list of the target population.
What is a strength of systematic sampling?
Unbiased.
The first item is usually selected at random.
Objective method.
What is a limitation of systematic sampling?
Time and effort.
A complete list of the population is required.
May as well use random sampling.
Stratified sample
Sample reflects proportions of people in certain subgroups (strata) within a population.
How is a stratified sample technique used?
Subgroups (strata) are identified e.g. gender or age. The relative percentages of the subgroup in the population are reflected in the sample.
What is a strength of stratified sampling?
Representative method.
The characteristics of the target population are represented.
Generalisability more likely than other methods.