KA3.2c - Sampling Flashcards
KA3.2 - Experimentation (8 cards)
Describe the term ‘representative sample’
a subset of a population that mirrors the characteristics of the larger group it’s drawn from
e.g. a smaller group that reflects the whole population
Why is a representative sample selected in an investigation?
It is impractical to measure every individual in a population, so a representative sample should be selected.
Explain how an appropriate sample size is determined?
the natural variation in the whole population determines the appropriate sample size; more variable populations require a larger sample size.
e.g. it depends on what you’re sampling
What characteristics should a representative sample share with the population?
Share the same mean and the same degree of variation about the mean as the population as a whole
State the three sampling methods
- Random
- Systematic
- Stratified
Define ‘random sampling’
members of the population have an equal chance of being selected.
Define ‘systematic sampling’
members of a population are selected at regular intervals
Define ‘stratified sampling’
the population is divided into categories that are then sampled proportionally
