Probability

• Experiment


  A repeatable process that gives rise to a number of outcomes
• Event


  A collection of one or more outcomes
• Sample space


  The set of all possible outcomes
• Probability


  Can be written as decimals or fractions, range from 0 (impossible) to 1 (certain)
• Calculating probability


  Number of possible outcomes in the event / Total number of possible outcomes
• Time taken to complete a number puzzle


  • 5 ≤ t < 7
  • 7 ≤ t < 9
  • 9 ≤ t < 11
  • 11 ≤ t < 13
  • 13 ≤ t < 15
• Probability of a student finishing the number puzzle in under 9 minutes
• Probability of a student finishing the number puzzle in over 10.5 minutes
• Venn diagram


  Represents events graphically, can show frequencies or probabilities in the regions
• Tree diagram


  Shows the outcomes of two or more events happening in succession
• Calculating probability of two beads being different colours

  P(green then blue) + P(blue then green) = (7/12 * 5/11) + (5/12 * 7/11) = 35/66
• Mutually exclusive events


  Events which have no outcomes in common
• Independent events


  One event has no effect on another
• Probability of a student watching TV show B or C or both
• Watching TV show A and watching TV show B are not statistically independent