Introduction
Probability sampling means every member of the population has a known chance of being selected.
This method reduces bias and improves research quality.
Types of Probability Sampling
1. Simple Random Sampling
Every person has an equal chance of selection.
Example:
Picking names randomly from a list.
2. Systematic Sampling
Researchers select every nth participant.
Example:
Selecting every 10th customer entering a supermarket.
3. Stratified Sampling
The population is divided into groups (strata).
Example:
Separating participants by gender before selecting samples.
4. Cluster Sampling
Researchers select entire groups instead of individuals.
Example:
Selecting three schools and surveying all students in those schools.
Advantages
- More representative
- Lower risk of bias
- Better for statistical analysis
Practice Activity
Identify the sampling method:
“A researcher selects every 5th student entering the library.”