Sampling Methods Flashcards
Target population
Every individual in the group you are going to study. Done by generalisation
What is a sample
A small group of people who represent the target population and who are studied. Has to be represented otherwise it affects internal validity
What is the critical feature of a sample?
If the sample is representative then you can generalise the results of the study to the wider population
Random sampling
Each member of the target population has a mathematically equal chance of being in the experimenters sample
Sampling frame
The complete list of all the members. All names are assigned a number then selected by an unbiased means
Unbiased ways of creating a sampling frame
Computer based or lottery method (picked out a hat)
Advantages of random sampling
No bias
Disadvantages of random sampling
-Impractical takes time and effort to put sampling frame together
-not completely representative (can use a bigger sample)
Opportunity sampling
The researcher directly asks the available members of the target population to take part in the research
How is opportunity sampling conducted
The researcher goes somewhere they are likely to find their target population
Advantages of opportunity sampling
-recruit lots of people very quickly
-cheap
-useful for naturalistic experiments
Disadvantages of opportunity sampling
Unrepresentative: very bias cannot confidently representative
Volunteer sampling
Self selecting sample
How is volunteer sampling conducted
Participants actively voulenteer to take part after finding out about the research. Researcher picks most appropriate for the study.
Advantages of volunteer sampling
-you don’t have to go out looking for people
-can reach wide audience
-convenient and economical
Disadvantages of volunteer sampling
-volunteer bias
-people might not volunteer
-specific volunteers
-sampling bias
Systematic sampling
Selecting names from the sampling frame at regular intervals e.g every 5th name
Advantages of systematic Sampling
-simple
-objective system
-reduces researcher bias
Disadvantages of systematic sampling
-inefficient
-not truly random
Stratified sampling
Select participants from differant sub-groups (strata) in the target population in proportion to the subgroups frequency to the population
Advantages of stratified sampling
Most representative
Disadvantages of stratified sampling
-knowledge of population characteristics required
-time consuming
Types of sampling
-stratified
-ramdon
-volunteer
-sytematic
-opportunity
