Year 1 Statistics Flashcards
(53 cards)
What is a population?
The whole set of items that are of interest.
What is a census?
Measure of every member of the population.
What is a sample?
Taken from a subset of the population, used to find out information from the population as a whole.
What is the advantage 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 large data.
What are the advantages of a sample?
- Less time-consuming and cheaper.
- Fewer have to respond.
- Less data to process.
What are the disadvantages of a sample?
- Data may not be accurate.
- Sample may not be large enough to give information of small sub-groups of the population.
What are sampling units?
Individual units of a population.
What is a sampling frame?
Sampling units of a population.
What are the types of random sampling?
Simple random sampling, Systematic sampling and Stratified sampling.
What is simple random sampling?
Ordered list, generate a random number using a calculator/computer or members are picked from a ‘hat’ (Lottery sampling).
What is systematic sampling?
Sample taken at regular intervals from an ordered list.
Divide the population by sample size and randomly generate the start number.
What is stratified sampling?
When the population are divided into stratas, a random sample is taken from each.
(Number in strata / Number in population) x Sample size.
What are the advantages of simple random sampling?
- Free from bias.
- Easy and cheap for a small sample.
- Each sampling unit has an equal chance of selection.
What are the disadvantages of simple random sampling?
- Time-consuming and expensive for a large sample size.
- A sampling frame is needed.
What are the advantages of systematic sampling?
- Simple and quick.
- Suitable for large samples.
What are the disadvantages of systematic sampling?
- Sampling frame needed.
- Introduces bias if the sampling frame is not random.
What are the advantages of stratified sampling?
- Accurately reflects the population structure.
- Guarantees proportional representation.
What are the disadvantages of stratified sampling?
- Population must be classified into stratas.
What are the types of non-random sampling?
Quota sampling and Opportunity sampling.
What is Quota sampling?
Interviewers select a sample that reflects the characteristics of the whole population.
The population is divided into groups given characteristics.
What is opportunity sampling?
Taking a sample from people who are available and fit the criteria.
What are the advantages of quota sampling?
- A small sample is still representative of the population.
- No sampling frame is needed.
- Quick, easy and inexpensive.
- Easy comparison between different groups.
What are the disadvantages of quota sampling?
- Non-random sampling introduces bias.
- Must be divided into groups which can be costly and inaccurate.
- Increasing the scope of the study increases the number of groups, adding time and expense.
