Sample Selection and Technique

Question 1

Random Sample

Answer 1

Sample produced using a random technique so every member of the target population has an equal chance of being selected.

Question 2

Random Sample +/-

Answer 2

+ Unbiased as all members have an equal chance of being selected.

• Takes more time and effort than other techniques as you need to obtain a list of all the members of your target population, then identify the sample and then ask the people if they would like to take part.

Question 3

Stratified Sample

Answer 3

PP selected from different subgroups in the target population in proportion to the subgroups frequency in that population.

Question 4

Stratified Sample +/-

Answer 4

+ Specific subgroups can be chosen according to the variables considered to be important by the researcher. This increases control over possible extraneous variables.

• Decision about which subgroups to use may be biased, thus reducing the representativeness of the sample.

Question 5

Volunteer Sample

Answer 5

A sample of participants produced by asking for people willing to take part.

Question 6

Volunteer Sample +/-

Answer 6

+ Convenient way to find willing PP. Researchers need committed PP for lengthy studies and those that volunteer are more likely to stay in the study.

• Biased as volunteer PP are likely to be more highly motivated and/or with extra time on their hands than the population in general (volunteer bias).

Question 7

Opportunity Sample

Answer 7

PP produced by selecting people who are most easily available at the time of the study.

Question 8

Opportunity Sample +/-

Answer 8

+ Convenient as it takes little preparation and less time to locate sample than other techniques.

• Biased as sample is drawn from a specific part of the target population which has unique characteristics and is likely not representative.