AS Statistics: 1 Data Collection Flashcards
What is a population?
The whole set of items that are of interest.
What is a census?
A measure of 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 the advantages of a census?
- It should give a completely accurate result.
What are the disadvantages of a census?
- Time-consuming and expensive.
- Cannot be used when the testing process destroys the item.
- Hard to process a large quantity of data.
What are the advantages of a sample?
- Less time consuming and expensive than a census.
- Fewer people have to respond.
- Less data to process than a census.
What are the disadvantages of a sample?
- The data may not be as accurate.
- The sample may not be large enough to give information about small sub-groups of the population.
What are sampling units?
Individual units of a population.
What is a sampling frame?
When sampling units are individually named or numbered to form a list.
What is simple random sampling?
Where every sample has an equal chance of being selected.
What are the advantages of simple random sampling?
- Free of bias.
- Easy and cheap to implement for small populations and small samples.
- Each sampling unit has a know and equal chance of selection.
What are the disadvantages of simple random sampling?
- Not suitable when the population size or the sample size is large.
- A sampling frame is needed.
What is systematic sampling?
When elements are chosen at regular intervals from an ordered list.
What are the advantages of systematic sampling?
- Simple and quick to use.
- Suitable for large samples and large populations.
What are the disadvantages of systematic sampling?
- A sampling frame is needed.
- It can introduce bias if the sampling frame is not random.