sampling methods

Question 1

outline simple random sampling

Answer 1

uniquely number every member of a population and randomly selecting n different numbers using a random number generator or a form of lottery (where numbers are selected randomly)

Question 2

outline systematic sampling

Answer 2

To carry this out you would calculate the size of the interval (k=size of population / size of sample) and choose a starting point between 1 and then select every kth member after the first one

Question 3

outline quota sampling

Answer 3

the population is split into groups (like stratified sampling) and members of the population are selected until each quota is filled

Question 4

outline opportunity sampling

Answer 4

a sample is formed using available members of the population who fit the criteria

Question 5

advantages and disadvantages of simple random

Answer 5

• every member of population has an equal chance of being selected (UNBIASED)
• can be inconvenient if sample is spread over large area

Question 6

advantages and disadvantages of systematic sampling

Answer 6

• quality control on production line, should be unbiased
• if the interval coincides with a pattern, the sample could be biased

Question 7

advantages and disadvantages of stratified sampling

Answer 7

• categories are mutually exclusive.
  will give representative sample
• extra process of deciding who to survey can be expensive

Question 8

outline cluster sampling

Answer 8

divide population into clusters, randomly select clusters to use in the Sample. either use all people inside the cluster or randomly sample within cluster.

Question 9

advantages and disadvantages of cluster sampling

Answer 9

• more practical
• less representative
  not always natural to separate a sample into clusters.

Question 10

outline opportunity/convenience sampling

Answer 10

chose members of the population that are easiest to sample

Question 11

advantages/disadvantages of opportunity/convinience sampling

Answer 11

• data gathered quickly/easily
• isn’t random, can be very easily biased.
  no attempt to make sample representative

Question 12

advantages/disadvantages of quota sampling

Answer 12

• easy, non-response less of a problem as quota must be met
• biased, selection process isn’t random

Question 13

advantages/disadvantages of volunteer/self selection sampling

Answer 13

• requires little time/effort in finding sample members, as they come to you
• people who volunteer are less likely to not respond
• could be the only way to get people to take part in a survey
• there can easily be trends within the respondents, such as people having strong opinions which could lead to bias

Question 14

sampling methods that use a list of the whole population

Answer 14

simple random
systematic
stratified
cluster

Question 15

sampling methods that do not use a list of the whole population

Answer 15

opportunity/convenience
quota
volunteer/self selection