Year 1 Flashcards
In statistics, what is a population?
A whole set of items that are of interest.
What is a census?
An observation or 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 and disadvantages of a census?
Gives a completely accurate result.
However,
Is time consuming and expensive
Cannot be used when the testing process destroys the item
It is harder to process larger quantities of data.
What are the advantages and disadvantages of a sample?
Less time consuming and less expensive than a census
Fewer people are needed to respond
There is less data to process than a census
However,
Data may not be accurate
The sample group may not be large enough to represent the population.
What is a sampling unit?
Individual units of a population.
What is random sampling?
Where every member of the population has an equal chance of being selected. The sample should be representative of the population. Random sampling removes bias from a sample.
What are the 3 methods of random sampling?
Simple random sampling
Systematic sampling
Stratified sampling
What is a brief description of simple random sampling?
A random sample of size n is one where every sample of size n has an equal chance of being selected
Brief description of stratified sampling?
The population is divided into mutually exclusive strata and a random sample is taken from each. The proportion of each strata samples should be the same.
Brief description of systematic sampling?
Required elements are chosen at regular intervals from an ordered list.
Advantages and disadvantages of simple random sampling?
Removes bias
easy and cheap to implement into small populations
Each sampling unit has an equal chance of selection
However,
not suitable for larger sample/population sizes
A sampling frame is needed
Advantages and disadvantages of systematic sampling?
Simple and quick to use
suitable for large sample/population sizes
However,
Requires a sampling frame
Can introduce bias if the sampling frame is not random
Advantages and disadvantages of stratified sampling?
Sample accurately reflects the population
Guarantees proportional representation of groups within a population
However,
Population must be clearly classified into distinct strata
Selection within each strata suffers from the same disadvantages as simple random sampling.
What are the 2 types of non-random sampling?
Quota sampling
Opportunity sampling