1.1 Populations and Samples

What is a census?

an observation of every member within 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.

Advantages of a census

Should give a completely accurate result

Disadvantages of a census

Time consuming, expensive

Cannot be used when the testing process destroys the item

Hard to process large quantitiy of data

Advantages of a Sample

Less time consuming, Less expensive

Easier to process smaller quantitiy of data

Fewer people have to respond

Disadvantages of a Sample

Data may not be as accurate

Sample may not be large enough to give information about small sub-groups of the population.

What is a sampling unit

The individual unit of a population e.g. A person

Sampling units are often individually named or numbered to form a list. This is called a sampling frame