SAMPLING AO1 & AO3

Question 1

Sampling techniques

Answer 1

• A sample is taken from a target population
• Must be a representative sample = generalise findings
  Random, systematic, stratified, opportunity and volunteer

Question 2

Random sample

Answer 2

Each person in the sampling frame has an equal chance of selection e.g. drawing names from a hat or computer generator

Question 3

Random sampling ADVANTAGE

Answer 3

• Unbiased selection
• Laws of probability says the researcher will normally get a representative sample

Question 4

Random sampling DISADVANTAGE

Answer 4

• Chance that the sample is not representative = can’t generalise

Question 5

Systematic sample

Answer 5

• Taking every nth person in sampling frame and selecting them for the sample.
• E.g. every 5th person

Question 6

Systematic bias EVA ADVANTAGE + DISADVANTAGE

Answer 6

+ Avoids bias as no control over who is selected
+ Laws of probability says the researcher will normally get a representative sample

• Chance that the sample is not representative = can’t generalize
• Not as objective as random sampling because research may decide on how people are listed before selection and the nth number used

Question 7

Stratified sample

Answer 7

• Sampling frame has been divided into groups that the research wants to make sure are represented in final sample
• A certain number of pts are selected from these groups (usually randomly) so that they are proportionately represented in the sample

Question 8

Stratified sample EVA ADVANTAGE + DISADVANTAGE

Answer 8

+ Ensures the sample is representative
+ objective because once the sampling has been stratified – normally left to chance (random sample) who is selected

• Time consuming than other techniques
• Researcher may not identify all the key characteristics for stratification meaning the sample is not representative

Question 9

Opportunity sample

Answer 9

Made up of pts that have been selected because they are convenient and available

Question 10

Opportunity sample EVA ADVANTAGE + DISADVANTAGE

Answer 10

+ Easy and convenient
+ Least time consuming

• Biased because the target population is so small
• Biased because only certain types of people will volunteer to be chosen e.g. free time or interested in research
• Researcher may show bias when selecting the pts