2.4.7—Sampling techniques
- Syllabus
- First assessment 2027
- Objective
- 2.4.7
- Level
- SL
Sampling is the bridge between a target population and actual participants
A sample is selected from a target population so that a study can collect evidence within practical limits. Opportunity and volunteer samples are convenient; random and stratified methods aim for better representation; snowball sampling reaches hidden populations.
Choose the method from the research aim and access conditions. A random draw can still be unbalanced by chance, while a stratified design matches selected population proportions only for characteristics that were measured and used.
A study of an uncommon group may begin with one trusted participant and use referrals, gaining access but narrowing the network. A campus volunteer advert is faster but can overrepresent people who are willing and interested in the topic.
A large sample is not automatically representative. State who could be selected, who was actually selected, and how that route limits generalisation and introduces bias.