Types Of Sampling

Question 1

Random sampling definition

Answer 1

Every item has an equal chance of being selected for the sample

Question 2

Non-random sampling definition

Answer 2

Sample selection is based on other factors than just random chance

Question 3

What are the 3 random sampling types?

Answer 3

• Simple random sampling
• Systematic sampling
• Stratified sampling

Question 4

Method for simple random sampling

Answer 4

• In the sampling frame, each item has identifying numbers
• Use a random number generator and ignore repeated numbers

Question 5

Advantages for simple random sampling

Answer 5

• Bias free
• Easy and cheap to implement
• Each number has a known equal chance of being selected

Question 6

Disadvantages for simple random sampling

Answer 6

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

Question 7

Method for systematic sampling

Answer 7

• Required elements are chosen at regular intervals in an ordered list
• Take every nth elements where: n = population size / sample size (n), starting at random item between 1 and n

Question 8

Advantages for systematic sampling

Answer 8

• Simple & quick
• Suitable for large samples/population

Question 9

Disadvantages for systematic sampling

Answer 9

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

Question 10

Method for stratified sampling

Answer 10

• The population is divided into groups (strata) and a simple random sample is carried out in each group
• Same proportion
• Used when the sample is large and the population naturally divides into groups
• Sample size (n) / population size (N)

Question 11

Advantages for stratified sampling:

Answer 11

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

Question 12

Disadvantages for stratified sampling

Answer 12

• Population must be clearly classified into distinct strata
• Sampling frame needed

Question 13

What are the 3 non-random sampling types?

Answer 13

• Quota sampling
• Opportunity/convenience sampling
• Cluster sampling

Question 14

Method for quota sampling

Answer 14

• Population is divided into groups according to characteristic
• A quota of items/set of people in each group is set to reflect the group’s population

Question 15

Advantages for quota sampling

Answer 15

• Allows small sample to still be representative of population
• No sampling frame needed
• Quick & easy
• Allows for easy comparison between different groups in population

Question 16

Disadvantages for quota sampling

Answer 16

• It is non-random so it introduces bias
• Population must be divided into groups which is expensive
• Non-responses are not recorded

Question 17

Method for opportunity/convenience sampling

Answer 17

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

Question 18

Advantages for opportunity/convenience sampling

Answer 18

• Easy to carry out
• Cheap

Question 19

Disadvantages of opportunity/convenience sampling

Answer 19

• Unlikely to provide a representative sample
• Highly dependent of the individual researcher (the time of day)

Question 20

Method for cluster sampling

Answer 20

• Non-random stratified sampling
• Define each cluster (should be representative of population)
• Collect random samples from each cluster

Question 21

Advantages for cluster sampling

Answer 21

• No sampling frame needed
• Cheap

Question 22

Disadvantages for cluster sampling

Answer 22

Unlikely to provide representation of the sample because clusters tend to have similar characteristics, resulting in over representation within a cluster