1.3 Non-random Sampling

Question 1

What is quota sampling

Answer 1

Population divided into groups according to characteristics

A quota of items in each group is set to try & reflect the group’s proportion in the whole population (quotas are calculated in same way as stratified sampling)

Interviewer selects the actual sampling units until the quotas are reached
(once a quota is full, ignore subsequent sampling units that also meet the characteristic)

Question 2

Advantage of a quota

Answer 2

• Allows the sample to be representative of population
• No sampling frame required, which can be difficult or impossible to obtain in some situations
• Relatively quick, easy & inexpensive to administer

Question 3

Disadvantages of a quota

Answer 3

• Non-random so likely to be biased
• Population must be divided into groups, which can be costly or inaccurate
• Can depend on knowledge/expertise of researcher

Question 4

What is opportunity/convenience sampling

Answer 4

In this method, the researcher chooses individuals who are available/accessible at the time, rather than selecting them at random or based on any specific characteristics of the population

eg. researcher might choose participants walking by in a public space or students in particular class

Question 5

Advantage of opportunity sampling

Answer 5

• No sampling frame required, which can be difficult or impossible to obtain in some situations
• Easy & inexpensive to administer

Question 6

Disadvantages of opportunity sampling

Answer 6

• Non-random so likely to be biased
• Unlikely to provide a representative sample
• Highly dependent on individual researcher

Question 7

Full marks layout for quota questions

Answer 7

• Add up all elements to create total pop ___ + ___ + ___ = P
• 1st element/P all multiplied by sample asked for
  repeat for all elements
• The researcher selects and [context of Q] the [items] until the quotas of ___ [trout eg], ___ [bass], ___ [pike] have been filled. Ignore any subsequent [items] once a quota is full