Statistics Year 1: POPULATIONS AND SAMPLES

sections 1 populations and samples

Population

a whole set of items of interest

information obtained from a population

raw data

census

observes or measures every member of a population

sample

a selection of observations taken from a subset of the population, which is used to find out information about the whole population

advantages of doing a census

gives completely accurate results

disadvantages of doing a census

time-consuming and expensive

cannot be used when the testing process destroys the item

hard to process large quantities of data

advantaged of using samples

less time-consuming and expensive than a census

fewer people have to respond

less data to process than a census

disadvantage of using samples

data may not be representative of the whole population

samples may not be large enough to give information about small subgroups of the population

sample size can affect the validity of any conclusion drawn

sample size depends on required accuracy and available resources

larger samples are more accurate but require more resources

varied populations need larger samples than uniform populations

different samples can lead to different conclusions due to the natural variations in a population

individual units of a population

sampling units

sampling units of a population are often individually named or numbered to form a list called

sampling frame