what is a population?
the whole set of items that are of interest
what does a census do
observes or measures every member of the 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 is an advantages of a census?
it should give a completely accurate result
what are disadvantages of a census
-time consuming
-cannot be used when the testing process destroys the item
-hard to process large quantity of data
what are advantages of a sample
-less time consuming and expensive than a census
-fewer people have to respond
-less data to process than in a census
what are disadvantages of a sample
-the data may not be accurate
the sample may not be large enough to give information about small sub groups of the population
how does the size of the sample affect the validity of any conclusions drawn
-the larger the sample the more accurate the data
-the smaller the sample the less accurate the data
what are individual units in population known as
sampling units
what often occurs to sampling units
they are numbered or named to form a list called a sampling frame.
if the population is varied and not uniform, what effect does this have on the sample size
the sample size would need to be larger than if the population were uniform
