Types of Sampling (scientific processes)

Random Sampling

Every member of a population has an equal chance of being selected

e.g. Pulling names out of a hat, or random number generators

Advantages and disadvantages of Random Sampling

Advantages

• best chance of an unbiased sample; equal chance of being selected

Disadvantages

• selecting a sample from large population can be time consuming

• can still get unbiased results

Systematic Sampling

Uses predetermined system to select every nth member of target population

e.g. every 4th house on a street (list in a specific order, then use intervals to randomly assign the sample)

Advantages and disadvantages of Systematic Sampling

Advantages

• Avoids researcher bias as objective system is used

• Fairly representative

Disadvantages

• Not strictly random as not everyone has an equal chance of being selected

Stratified Sampling

Composition of the sample reflects the proportions of people in certain strata within target population. Identify different strata and their relative proportions, then randomly select that number from each strata

Advantages and disadvantages of Stratified Sampling