Sampling Flashcards
What is simple random sampling and how is it done
- Every sample has an equal chance of being selected
- In sampling frame each item is given a number, using a random number generator to select sample
What is systematic sampling and how is it done
- Required elements are chosen at regular intervals in ordered list
- Take every ‘Kth’ element where K = whole population size/sample size, start at random number between 1-K and add K each time
What is stratified sampling sampling and how is it done
- Population is divided into groups and a simple random sample is carried out in each group
- Each group is identified, the same proportion of sample size/whole population size is sampled from each strata (distinct group)
What is cluster sampling and how is it done
The population is split into clusters based on convenience, then clusters are randomly chosen to study further
What is quota sampling and how is it done
- The whole population is divided according to a characteristic
- A quota of items/people in each group is set to try and reflect the groups proportion in the whole population
- The interview selects the actual sampling units
What is opportunity sampling and how is it done
- A sample taken from people who are available at the time of the study who meet the criteria
What are the advantages of simple random sampling
- Bias free
- Easy and cheap
- Equal chance for every individual
What are the advantages of systematic sampling
- Simple and quick
- Suitable for large samples
What are the advantages of stratified sampling
- Reflects population structure
- Guarantees proportional representation of groups within population
What are the advantages of cluster sampling
- More practical and easy
- Cheaper
What are the advantages of quota sampling
- Quick, easy, inexpensive
- Allows for easy camparison between different groups in population
What are the advantages of opportunity sampling
- Easy to carry out
- Inexpensive
What are the disadvantages of simple random sampling
- Not suitable when population size is large
- Sampling frame needed
What are the disadvantages of systematic sampling
- Sampling frame needed
- Can introduce bias if sampling frame is not random
What are the disadvantages of stratified sampling
- Population must be classified into different strata
- Sufferes same disadvantages as simple random sampling for each strata
What are the disadvantages of cluster sampling
- Could cause bias since some of the population is not included in the sampling frame
What are the disadvantages of quota sampling
- Non random sampling can introduce bias
- Costly or inaccurate to divided population into groups
- Non repsonses are not recorded
What are the disadvantages of opportunity sampling
- Unlikely to provide representative sample
- Highly dependent on individual researcher
