Study Variation

• What do you have to do to study variatioN?

  Look at a SAMPLE of the population, not the whole thing
• Why do you only sample a population when studying variation, instead of looking at whole population?

  Too time-consuming or impossible to catch all individuals
• What are samples used as?


  Models for the whole population
• What is important?


  Sample must represent whole population - because sample data used to draw conclusions about whole population
• What must be tested?

  any patterns observed are tested to make sure not due to change
• How do you make sure sample is not biased?

  • Random
  • Random number generator to pick random sample sites
• What should you do to ensure any variation observed in the sample is NOT due to chance?

  Important to analyse the results statistically = allows you to be more confident that results are true and reflect what going on in whole pop
• What can you use the mean to do?

  Tel if there is variation between samples
• What will most samples include?

  Values either side of the mean - so you end up with a bell-shaped graph- this is called a normal distribution
• What is a normal distribution like?


  Symmetrical about the mean