Target population is divided into groups. The sample selected is in the proportion to which they occur in the population. E.g., if 20% were male, in a sample of 100, 20 would be male.
What is a strength of stratified sampling?
It reduces sampling bias. This is a strength as there is better generalisability and better representation of the population.
What is a weakness of stratified sampling?
Researchers have to select relevant strata groups. This is a weakness as it can be difficult and time-consuming.
