Sampling

Question 1

Census

Answer 1

• Observes or measures every member of a population.

Question 2

Sample

Answer 2

• Selection of observations taken from a subset of the population which is used to find out information about the population as a whole.

Question 3

Advantage of Census

Answer 3

• Gives a completely accurate result.

Question 4

Disadvantages of Census

Answer 4

• Time Consuming
• Expensive
• Can’t be used when testing process destroys the item.

Question 5

Advantages of Sample

Answer 5

• Less time consuming and expensive than a census.
• Fewer people have to respond.
• Less data to process than in a census.

Question 6

Disadvantages of Sample

Answer 6

• Data may not be as accurate.

- Sample may not be large enough to give information about small sub-groups of the population.

Question 7

Simple Random Sample

Answer 7

• Every sample of size has an equal chance of being a selected.

Question 8

How Carry Out Simple Sample?

Answer 8

• Sampling frame, each person in SF allocated a unique number and they’re chosen at random.

Question 9

Systematic Sampling

Answer 9

• Required elements are chosen at regular intervals from an ordered list.
• Take every fifth person from a sample.

Question 10

Stratified Sampling

Answer 10

• Population is divided into mutually exclusive strata and a random sample is taken from each.

Question 11

Advantages of Simple Random Sampling

Answer 11

• Free of Bias
• Easy and cheap to implement for small populations/samples.
• Each sampling unit has a known and equal chance of selection.

Question 12

Disadvantages of Simple Random Sampling

Answer 12

• Not suitable when the population size or the sample size is large as it is potentially time consuming and expensive.
• Sampling frame is needed (Electoral Roll).

Question 13

Advantages of Systematic Sampling

Answer 13

• Simple and quick to use.

- Suitable for large sample and populations.

Question 14

Disadvantages of Systematic Sampling

Answer 14

• Sampling frame is needed.

- Can introduce bias if the sampling frame is not random.

Question 15

Advantages of Stratified Sampling

Answer 15

• Sample accurately reflects the population structure.

- Guarantees proportional representation of groups within a population.

Question 16

Disadvantages of Stratified Sampling

Answer 16

• Population must be clearly classified into distinct strata.
• Selection within each stratum suffers same Ds as SRS; not suitable when large populations/samples.

Question 17

Quota Sampling

Answer 17

• An interviewer selects a sample that reflects the characteristics of the whole population.
• Divided into groups according to characteristics.
• Meet people, allocate them to the appropriate quota until its fulfilled.

Question 18

Opportunity Sampling

Answer 18

• Consists of taking the sample from people who are available at the time the study is carried out and who fit the criteria you are looking for.
• Pick the first 20 people you see.

Question 19

Advantages of Quota Sampling

Answer 19

• Allows a small sample to still be representative of the population.
• No sample frame required.
• Quick, easy and inexpensive.
• Allows for easy comparison between different groups within a population.

Question 20

Disadvantages of Quota Sampling

Answer 20

• NRS can introduce bias.
• Population must be divided into groups, costly or inaccurate.
• Increasing scope of study increases number of groups, adds time and expensive.
• Non responses are not recorded.

Question 21

Advantages of Opportunity Sampling

Answer 21

• Easy to carry out

- Inexpensive.

Question 22

Disadvantages of Opportunity Sampling

Answer 22

• Unlikely to provide a representative sample.

- Highly dependent on individual researcher.