data handling notes

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Sampling and bias

  • sample data must be representative
  • the population is the whole group you want to find out about
  • often you can't survey the whole population
  • a sample is a small group from the population
  • for a sample to be representative it needs to be: a random sample (every member has an equal chance of being in it) and big enough for the size of the population
  • to spot bias you need to think about when, where and how the sample is taken and how many members are in it
  • if certain groups are excluded, the sample isn't random and that can lead to bias from things like age, gender and different interests
  • if the sample is too small, it's also likely to be biased

Sampling methods

random sampling

  • assign a number to every member of the population
  • create a list of random numbers
  • match the random numbers to members of the population

stratified sampling

  • find the proportion…


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