Data Collection

• A population is the whole set of items that are of interest.
• A census observes or measures every member of a population.
• A sample is a selection of observations taken from a subset of the population which is used to find out more information about the population as a whole.
• Census Advantage: It should give a completely accurate result.
• Census Disadvantages:

  1. Time consuming and expensive.
  2. Cannot be used when the testing process destroys the item
  3. Hard to process large quantities of data
• Sample Advantages:

  1. Less time consuming and expensive than a census
  2. Fewer people have to respond
  3. Less data to process than in a census
• Sample Disadvantages:

  1. The data may not be as accurate
  2. The sample may not be large enough to give information about small sub-groups of the population
• Sampling units are individual units of a population.
• Sampling frames are where sampling units of a population are individually named/numbered to form a list.
• Quantitative data / variables is data / variables associated with numerical observations.
• Examples of Quantitative data includes shoe size as you can give a number to it.
• Qualitative data / variables is data / variables with non-numerical observation.
• Examples of Qualitative data includes hair colour as you can’t assign it a number.
• A continuous variable is a variable that can take any value.
• A discrete variable is a variable that can only take specific values in a given range.