Sampling Flashcards
What are the 3 methods of random sampling?
- Simple random
- Systematic sampling
- Stratified sampling
What is simple random sampling?
Where every sample has equal chance of being selected
What is systematic sampling?
The elements are chosen at regular intervals from an ordered list.
What is stratified sampling?
Population is split into groups, and a random sample is taken from each.
Advantages of simple random sampling?
- Free of bias
- Easy and cheap
- Each thing has an equal chance of selection
Disadvantages of simple random sampling?
- Not suitable for large pops.
- Sampling frame needed.
Advantages of systematic sampling?
- Simple and quick
- Suitable for large pops.
Disadvantages of systematic sampling?
- Sampling frame needed
- It can introduce bias if frame is not random
Advantages of Stratified sampling?
- Accurately reflects the pop.
- Guarantees proportional representation of those in pop.
Disadvantages of Stratified sampling?
- Pop must be classified
- Selection within groups has same disadvantages as simple random sampling
Types of non random sampling?
- Quota sampling
- Opportunity sampling
What is Quota sampling?
An interviewer would choose a sample that reflects the pop
What is Opportunity sampling?
When the sample is taken from people ready at the time & who fit the criteria
Advantages of Quota sampling?
- Allows a small sample to represent the whole pop
- No frame required
- easy and cheap
Disadvantages of Quota sampling?
- Possible bias
- Groups may be inaccurate
- Larger pop means more expensive
- Non responses are not recorded as such
