Statistical sampling - Topic 1

Question 1

Year 1 - Chapter 1

Simple Random

Answer 1

A simple random size of n is one where every sample of size n has an equal chance of being selected

Question 2

Year 1 - Chapter 1

Advantages and disadvantages of simple random

Answer 2

Advantages:

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

Disadvantages:

• Not suitable when the population size or the sample size is large as it is potenitally time consuming, disruptive and expensive
• A sampling frame is needed

Question 3

Year 1 - Chapter 1

Systematic sampling

Answer 3

The required elements are chosen at regular intervals from an ordered list

Question 4

Year 1 - Chapter 1

Advantages and disadvantages of systematic sampling

Answer 4

Advantages:

• Simple and quick to use
• Suitable for large samples and large populations

Disadvantages:

• A sampling frame is needed
• It can introduce bias if the sampling frame is not random

Question 5

Year 1 - Chapter 1

Stratified sampling

Answer 5

The population is divided into mutually exclusive strata and a random sample is taken from each

Question 6

Advantages and disadvantages of stratified sampling

Answer 6

Advantages:

• Sample accurately reflects the population structure
• Guarantees proportional representation of groups within a population

Disadvantages:

• Population must be clearly classified into distinct strata
• Selection within each stratum suffers from the same disadvantages as simple random sampling

Question 7

Year 1 - Chapter 1

Quota sampling

Answer 7

An interviewer or researcher selected a sample that reflects the characteristics of the whole population

Question 8

Year 1 - Chapter 1

Advantages and disadvantages of quota sampling

Answer 8

Advantages:

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

Disadvantages:

• Non-random sampling can introduce bias
• Population must be divided intro groups, which can be costly or inaccurate
• Increasing scope of study increases number of groups, which adds time and expenses
• Non-responses are not recorded as such

Question 9

Year 1 - Chapter 1

Opportunity sampling

Answer 9

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

Question 10

Year 1 - Chapter 1

Advantages and disadvantages of opportunity sampling

Answer 10

Advantages:

• Easy to carry out
• Inexpensive

Disadvantages:

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