Sampling Methods Flashcards
1
Q
What is a sample? (2)
A
- Ppts selected from target pop
2. Must aim to be representative of pop
2
Q
What is a target population?
A
A group to be studied
3
Q
What are some methods of samplig? (4)
A
- Random
- Stratified
- Volunteer
- Opportunity
4
Q
What is random sampling? Strengths & weaknesses?
A
- All members have equal chance of selection - Lottery method (assigned a number and drawn from a hat)
- Strengths
- Control ppt variables
- Representative sample - Weaknesses
- SAMPLE ERROR - some ppts may refuse to take part- can lead to invalid conc
5
Q
What is stratified sampling? Strengths and weaknesses?
A
- Identifying subgroups in pop based on shared characteristics and then taking a random sample from each that is proportional to its size in the pop
- Strengths
- Useful if subg may be misrepresented w standard random sampling
- Representative sample - Weaknesses
- Time-consuming
- SAMPLE ERROR - some ppts may refuse to take part- can lead to invalid conc
6
Q
What is a sample error?
A
Sample differs from qualities of target pop it intended to represent (affects external validity)
7
Q
What is volunteer sampling? Strengths and weaknesses?
A
- Advertising study so ppts can self-select to form the sample
- Strengths
- Minimal effort
- Most ethical, no pressure on ppts to take part - Weaknesses
- Less representative, not everyone in TP will see ad or want to respond
- Biased, volunteers tend to have a particular personality (ppt variable)
8
Q
What is opportunity sampling? Strengths and weaknesses?
A
- Using ppts available at the time
- Strengths
- Quick and simple - Weaknesses
- Biased, not every member of TP will be around
- May misrepresent subgroups, affects generalisability
- Unreliable bc findings may differ if replicated at a diff time
9
Q
What is a biased sample?
A
Sample which doesn’t reflect the characteristics of the TP
