1.2.4 Sampling methods

Question 1

What is random sampling

Answer 1

This method gives every member of the target group an equal chance of being selected for the sample (e.g. by assigning a number to each member, and then selecting from the pool at using a random number generator).

Question 2

What are the strengths and weakness of random sampling

Answer 2

Strengths - It is widely accepted that since each member has the same probability of being selected, there is a reasonable chance of achieving a representative sample.

Weakness’s - Small minority groups within your target group may distort results, even with a random sampling technique.

It can be impractical (or not possible) to use a completely random technique, e.g. the target group may be too large to assign numbers to.

Question 3

What is systematic sampling

Answer 3

A systematic method is chosen for selecting from a target group, e.g. every fourth person in a list could be used in the sample. It differs from random sampling in that it does not give an equal chance of selection to each individual in the target group.

Question 4

Strength’s and weakness’s of systematic sampling

Answer 4

Strength’s - Assuming the list order has been randomised, this method offers an unbiased chance of gaining a representative sample

Weakness - If the list has been assembled in any other way, bias may be present. For example if every fourth person in the list was male, you would have only males in your sample.

Question 5

What is stratified sampling

Answer 5

Here the sampler divides or ‘stratifies’ the target group into sections, each showing a key characteristic which should be present in the final sample. Then each of those sections is sampled individually. The sample thus created should contain members from each key characteristic in a proportion representative of the target population.

Question 6

What are the strengths and weakness’s of stratified sampling

Answer 6

Strengths - It avoids the problem of misrepresentation sometimes caused by purely random sampling.

Weakness’s - It takes more time and resources to plan.

Care must be taken to ensure each key characteristic present in the population is selected across strata, otherwise this will design a biased sample.

Question 7

What is opportunity sampling

Answer 7

Participants who are both accessible and willing to take part are targeted e.g first 10 people to walk into the room

Question 8

Strengths and weakness’s of opportunity sampling

Answer 8

Strengths - easy and inexpensive to do.

Weakness’s - The consequent sample may not be representative as it could be subject to bias (e.g. the conveniently located employer may undertake a selection process for job applicants, making it likely that employees possess certain similar characteristics that are unrepresentative of the wider target group).

Question 9

What is volunteer sampling

Answer 9

Here the sample consists of people who have volunteered to be in the study.

Question 10

Strengths and weakness of volunteer sampling

Answer 10

Strength - This often achieves a large sample size through reaching a wide audience, for example with online advertisements.

Weakness - Those who respond to the call for volunteers may all display similar characteristics (such as being more trusting or cooperative than those who did not apply) thus increasing the chances of yielding an unrepresentative sample.