Sampling

Question 1

What is simple random sampling and how is it done

Answer 1

• 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

Question 2

What is systematic sampling and how is it done

Answer 2

• 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

Question 3

What is stratified sampling sampling and how is it done

Answer 3

• 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)

Question 4

What is cluster sampling and how is it done

Question 5

What is quota sampling and how is it done

Answer 5

• 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

Question 6

What is opportunity sampling and how is it done

Answer 6

• A sample taken from people who are available at the time of the study who meet the criteria

Question 7

What are the advantages of simple random sampling

Answer 7

• Bias free
• Easy and cheap
• Equal chance for every individual

Question 8

What are the advantages of systematic sampling

Answer 8

• Simple and quick
• Suitable for large samples

Question 9

What are the advantages of stratified sampling

Answer 9

• Reflects population structure
• Guarantees proportional representation of groups within population

Question 10

What are the advantages of cluster sampling

Answer 10

• More practical and easy
• Cheaper

Question 11

What are the advantages of quota sampling

Answer 11

• Quick, easy, inexpensive
• Allows for easy camparison between different groups in population

Question 12

What are the advantages of opportunity sampling

Answer 12

• Easy to carry out
• Inexpensive

Question 13

What are the disadvantages of simple random sampling

Answer 13

• Not suitable when population size is large
• Sampling frame needed

Question 14

What are the disadvantages of systematic sampling

Answer 14

• Sampling frame needed
• Can introduce bias if sampling frame is not random

Question 15

What are the disadvantages of stratified sampling

Answer 15

• Population must be classified into different strata
• Sufferes same disadvantages as simple random sampling for each strata

Question 16

What are the disadvantages of cluster sampling

Answer 16

• Could cause bias since some of the population is not included in the sampling frame

Question 17

What are the disadvantages of quota sampling

Answer 17

• Non random sampling can introduce bias
• Costly or inaccurate to divided population into groups
• Non repsonses are not recorded

Question 18

What are the disadvantages of opportunity sampling

Answer 18

• Unlikely to provide representative sample
• Highly dependent on individual researcher