Sampling

Question 1

What is meant by the term ‘population’?

Answer 1

The group of individuals the researcher is interested in.

Question 2

What is meant by the term ‘sample’?

Answer 2

A smaller group taken from the population that the researcher is interested in.

Question 3

Why is it important that a sample is representative of the target population?

Answer 3

So that generalisations of the findings to the target population can be made.

Question 4

List the 5 sampling methods.

Answer 4

1. Opportunity
2. Random
3. Stratified
4. Systematic
5. Volunteer

Question 5

What is an ‘opportunity sample’?

Answer 5

The researcher recruits those people who are most convenient or most available e.g people walking by on the street, or students at your school.

Question 6

What is a strength of using an opportunity sample?

Answer 6

It is the easiest method as you are using the first suitable participants that you can find -which takes less time than other methods.

Question 7

What is a limitation of using an opportunity sample?

Answer 7

It can be biassed - the sample is drawn from a small part of the population and can often vary e.g location depending, time of day.

Question 8

What is a ‘random sample’? Give examples.

Answer 8

Methods include the lottery method e.g names out of a hat, a random number table, or a random number generator.

Question 9

What is a strength of using a random sample?

Answer 9

It is unbiased - all members of the target population and therefore have an equal change of selection.

Question 10

What is a limitation of using a random sample?

Answer 10

The researcher needs to have a list of all members of the population and contact those selected, which takes time.

Question 11

What is a ‘stratified sample’?

Answer 11

Subgroups (or strata) within a population are identified e.g gender, age groups.

Participants are obtained from each of the strata in proportion to their occurence in the population.

Selection from the strata is done using a random technique.

Question 12

What is a strength of using a stratified sample?

Answer 12

It is likely to be more representative than other methods as there is a proportional and randomly selected representation of subgroups.

Question 13

What is a limitation of using a stratified sample?

Answer 13

It can be time consuming to identify subgroups, then randomly select and contact participants.

Question 14

What is a ‘systematic sample’?

Answer 14

The use of a predetermined system to select participants e.g selecting every 3rd persom the list.

The numberical interval is applied consistently.

Question 15

What is a strength of using a systematic sample?

Answer 15

It is unbiassed - participants are selected using an objective system.

Question 16

What is a limitation of using a systematic sample?

Answer 16

It is not truly unbiassed/random unless a number is selected using a random method and the process is started with this person when selected.

Question 17

What is a ‘volunteer sample’?

Answer 17

Advertisement in a newspaper, online etc - ask those interested in taking part to contact you.

People offer to participate.

Question 18

What is a strength of using a volunteer sample?

Answer 18

It gives access to a variety of participants which may make the sample more representative and less bias.

Question 19

What is a limitation of using a volunteer sample?

Answer 19

The sample is still biassed as participants may have more time, more motivation or need the money which is a volunteer bais.

Question 20

Describe the ‘lottery method’.

Answer 20

• Each persons name is put in a loterry barrel or hat.
• Select the number of names required.

Question 21

Describe the ‘random number table method’.

Answer 21

• Print a table of random numbers.
• Each member of the population is given a number.
• Place your finger on a random number to select a starting point.
• Select everyone with the numbers in the table from that point.

Question 22

Describe the ‘random number generator method.’

Answer 22

• Every member of the population is given a number.
• Use a calculator or a computer program to generate a random number between 1 and 100.

Question 23

What is a sampling bias?

Answer 23

All sampling methods are biased and distorted in some way e.g opportunity sample only represents the people that were available to the researcher at the time.

Question 24

What is a volunteer bias?

Answer 24

The fact that people volunteer to take part in research are likely to be different to other members of the population and this distorts or biases the data they produce.