Populations and samples

• Define population

  The whole set of items that are of interest
• What I'd raw data?


  Information obtained from a population
• What does a census do?

  Observes or measures every member of 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
• What is an advantage of a census?

  Should give accurate results
• What are the disadvantages of a census?

  --> time consuming

  --> expensive

  --> hard to process large quantity of data
• What are advantages of a sample?

  --> less time consuming and expensive

  --> fewer people have to respond

  --> less data to process
• What are disadvantages of a sample?

  --> data may be less accurate

  --> sample may not be large enough to give information about small sub groups of the population
• What are sampling units?

  Individual units of a population
• Often sampling units of a population are individually named of numbered to form a list called a sampling frame