Data Collection (Sampling)

• Primary data - collected by ourself therefore more reliable.
• Secondary data - collected by someone else therefore less reliable.
• Census - data from EVERYONE in a population
• Sample - data from a subset of the population
• Advantages of a census:

  • more data
  • subsections are represented
• Disadvanatges of a census:

  • lots of data to process
  • more expensive
  • more time consuming
• Advantages of a sample:

  • cheaper
  • less time consuming
  • CAN be representative of population
• Disadvantages of sample:

  • data is not always representative of population
  • subsets may be missed out
• 7 types of sampling:

  • snowball
  • judgemental
  • cluster
  • systematic
  • unrestricted random
  • simple random
  • stratified
• When there is no list, we must ENSURE VARIETY to make it REPRESENTATIVE.
• What is a sample frame?


  A list of the population, from which we can take a sample.
• What can be done when there is no sample frame?


  • see if the electoral role can be used in replacement
  • otherwise, must ENSURE VARIETY in sample by considering other variables e.g age, gender.
• Exam technique for sampling:


  Because sampling takes long written answers, must include context throughout answers.