Research Methods: Sampling

Question 1

What is a target population?

Answer 1

• A large group of individuals that a researcher is interested in studying as a subset of the general population e.g. autistic children under 6, women in their thirties.
• Due to practical and economic reasons, it is not possible to include ALL the members of a target population, so a smaller sample is used (representative of the target population, allowing for generalisation).

Question 2

What is a random sample?

Answer 2

• Sample where all members of the target population have an equal chance of being selected.
  Method: Obtain a list of all the members in a target population and assign each member a number. Use the lottery method (e.g. pick numbers from a hat, random number generator) to select the sample.

Question 3

What is a systematic sample?

Answer 3

• Sample where every nth member of the target population is selected e.g. every 5th pupil on a school register.
  Method: A sampling frame is produced (an organised list of people in a target population e.g. alphabetical order). A sampling system is nominated (e.g. every 3rd or 6th person etc) and may begin randomly to avoid bias. The researcher works through the sample frame until it is complete.

Question 4

What is a stratified sample?

Answer 4

• A sophisticated form of sampling where the composition of a sample reflects the proportion of people in subgroups (strata) within the target population.
  Method: The researcher identified the different strata that make up the population, and the proportion of people needed to be representative are calculated. The participants that are needed to make up that strata are selected via random sampling.

Question 5

What is an opportunity sample?

Answer 5

• If the representative samples of a target population are difficult to obtain, the researcher may decide to chose anyone who is willing and AVAILABLE at the time of their study.

Question 6

What is a volunteer sample?

Answer 6

• Participants select themselves to be a part of the sample (self-selection).
• A researcher may place an advert in a newspaper or raise their hand when a researcher asks for participants.

Question 7

Give a strength and limitation for random sampling:

Answer 7

Strength:
- Potentially unbiased, meaning CVs and EVs are divided equally between the two groups, enhancing internal validity.

Limitation:
- Difficult and time consuming to obtain a full list of a target population.
- Samples may be unrepresentative as there is still the possibility that very similar members of a population could be chosen.
- Selected members of a population may refuse to take part - possibly leading to a volunteer sample.

Question 8

Give a strength and limitation of systematic sampling:

Answer 8

Strength:
- Method is objective, once the system for selection has been established the researcher has no control over who is chosen.

Limitation:
- Samples may be unrepresentative as there is still the possibility that very similar members of a population could be chosen.
- Selected members of a population may refuse to take part - possibly leading to a volunteer sample

Question 9

Give a strength and limitation of stratified sampling:

Answer 9

Strength:
- Representative sample as it is designed to accurately represent the composition of the target population, allowing for generalisation of findings.

Limitation:
- The identified strata cannot reflect all the ways that people are different , so a complete representation of the target population is not possible.
- Selected members of a population may refuse to take part - possibly leading to a volunteer sample

Question 10

Give a strength and limitation of opportunity sampling:

Answer 10

Strength:
- Convenient and less time consuming than other methods e.g. random sampling.

Limitation:
- Unrepresentative of the target population as the sample is drawn from a very specific area, so results cannot be generalised to the target population.
- The researcher has control over the selection of participants and may unconsciously/consciously inflict researcher bias e.g. avoid people that they do not like the look of.

Question 11

Give a strength and limitation of voluntary sampling:

Answer 11

Strength:
- Very easy to gather participants, with minimal effort from the researcher so it is less time consuming.
- The researcher ends up with more engaged Ps as they themselves have chose to be a participant.

Limitation:
- Volunteer bias- asking for volunteers may attract a certain ‘profile’ of people, one who is trying to please the researcher (may affect how results can be generalised).