what is the foundation of any statistical investigation
there being a group of something you want to find out about
what is the whole group called
a population
what would it make a population if the members were countable
it would make it a finite population
what is an infinite population
a population in which the members are uncountable
what is a census
- a survey of the whole population
- where you collect info from every member of a population
what is a survey
- a method of collecting information about a population
- where you question people or examine items
what is the advantage that comes with using surveys
- it is an accurate representation of the population
- as every member has been surveyed
- meaning it is unbiased
what are the disadvantages that come with surveys
- for large populations it takes a lot of time and effort, sometimes money
- it can be difficult to make sure all the members are surveyed
- if some are missed it could be biased
- if the tested items are used up or damaged in some way by doing a census, it is impractical
what could you do if doing a census of a whole population is impractical
- you could find out about the population by questioning or examining a selected group
- called a sample
what are the advantages of a sample
- they are quicker and easier than a census
- its easier to get a hold of all the required info
- its the only option when surveyed items are used up or damaged
what are the disadvantages of a sample
- each possible sample will give different results, so you could just happen to select one which doesnt accurately reflect the population
- samples can be easily affected by sampling bias
what are the three things that should be done to avoid sampling bias
- select from the correct population and make sure no member is excluded
- select at random
- make sure all sample members respond
