Statistics definitions Flashcards
What is a population?
The whole set of items that are of interest.
What does a census do?
It measures every member of a population.
What is a sample?
A selection of observations taken from a subset of the population which is used to find out information about the population as a whole.
What are sampling units?
Individual units of a population.
What is a sampling frame?
A list of individually named or numbered sampling units of a population.
What are the three methods of random sampling?
- Simple random sampling
- Systematic sampling
- Stratified sampling
What is a simple random sample?
One where every sample has an equal chance of being selected.
What is a systematic sample?
One where the required elements are chosen at regular intervals from an ordered list.
What is a stratified sample?
One where the population is ordered into mutually exclusive strata and a random sample is taken from each.
What are the advantages of simple random sampling?
- Free of bias
- Easy and cheap for small populations and samples
- Each sampling unit has a known and equal chance of selection
What are the disadvantages of simple random sampling?
- Not suitable when the population or sampling size is large
- A sampling frame is needed
What are the advantages of systematic sampling?
- Simple and quick
- Suitable for large samples and populations
What are the disadvantages of systematic sampling?
- A sampling frame is needed
- It can introduce bias if the sampling frame is not random
What are the advantages of stratified sampling?
- Sample accurately reflects the population structure
- Guarantees proportional representation of groups within a population
What are the disadvantages of stratified sampling?
- Population must be clearly classified into distinct strata
- Selection within each stratum suffers from the same disadvantages as simple random sampling