Sampling Flashcards
(37 cards)
Population
The whole set of items that are of interest
Sample
Some subset of the population that represents the population
Census
Data collected from the entire population
Sampling frame
List of the samples
What are the advantages of a census?
- Completely accurate
What are the disadvantages of a census?
- Large volume of data to process
- Time-consuming
- Expensive
- Testing may lead to destruction
What are the advantages of sampling?
- Cheaper
- Quicker
- Less data to process
What are the disadvantages of sampling?
- May not be large enough to represent small strata
- May be inaccurate
Method of simple random sampling:
- Assign each item an identifying number
- Use a bias-free method like RNG to generate numbers
- Use these identifying numbers to select the items
What are the advantages of simple random sampling?
- No bias
- Cheap
- Easy
What are the disadvantages of simple random sampling?
- Not suitable for a large population
- Sampling frame is needed
Method of systematic sampling:
- Assign each item an identifying number
- Calculate the sampling interval by dividing the population size by the sample size you want eg. 500/100 = 5
- Choose a random starting point eg. 42
- Sample each item with an interval from the starting point eg. 47, 52, 57 and so on
What are the advantages of systematic sampling?
- Suitable for large population
- Quick
What are the disadvantages of systematic sampling?
- Sampling frame is needed otherwise it’s biased
Method of stratified sampling:
- Divide the sample size you want (1 strata) by the whole population size
- Multiply this by the other strata’s to identify how many people you need of each
What are the advantages of stratified sampling?
- Reflects population structure
- Guarantees proportional representation
What are the disadvantages of stratified sampling?
- Pop needs to be clearly divided eg. year groups in a school
Method of quota sampling:
- Determine your quota eg. 20 ppl from US, 20 ppl from UK
- Select people to fit into stratas of specific characteristics eg. Born in the UK, born in US
- Continue selecting until the quota is met
What are the advantages of quota sampling?
- A small sample can still be represented
- Sampling frame is not needed
- Quick
- Provides an easy comparison
What are the disadvantages of quota sampling?
- Biased
- Possible inaccurate division of strata
- Time-consuming
- Non-responses are not recorded
Method of self-selected sampling:
Samples are selected by the researcher
What are the advantages of self-selected sampling?
- Quick
- Easy
What are the disadvantages of cluster sampling?
- Unlikely to provide a representative sample
Method of opportunity sampling:
- Sample people that are available at the time of your study eg. First 20 people you see
