Population definition
The whole set of items that are of interest
Sample definition
Subset/part of the population intended to represent the whole population
Sampling frame definition
Sampling units of a population that are individually named or numbered to form a list
e.g: a phone directory
Sampling unit definition
Each individual thing in the population that can be sampled
e.g: To find out how many cars a family owns, the sampling unit would be the household rather than an individual because you don’t want to ask 2 people from the same household
Census definition
It is when data is collected from an entire population
Advantages of a census
- Representative of the entire population
- Should give completely accurate results
Disadvantages of a census
- Time consuming
- Expensive
- Cannot be used when testing involves destruction (when some of the data isn’t valid)
- Large volume of data to process
Advantages of a sample
- Cheaper
- Quicker
- Less data to process
Disadvantages of a sample
- Data may not be accurate
- Data may not be large enough to represent small sub-groups
Parameters definition
A calculation of the sample or population (usually the mean)
It is better if it is as close to the population as possible
Sampling error definition
Difference between mean of entire population and mean of sample
Bias definition
A systematic error in the collection of the sample
What can result in a biased sample?
- Small sample size
- A sample that is not representative of the population
