Probability is a fundamental concept that helps you understand and predict the likelihood of events occurring. It’s a measure of how likely something is to happen, expressed as a number between 0 and 1.

 

1.1 Definition of Probability

Probability is the ratio of favorable outcomes to the total number of possible outcomes, assuming all outcomes are equally likely.   For example, when you flip a fair coin, there are two possible outcomes: heads or tails. The probability of getting heads is 1/2 or 0.5, because there’s one favorable outcome (heads) out of two possible outcomes.

 

1.2 Key Terms in Probability

  • Event: A specific outcome or set of outcomes in an experiment or situation.
  • Sample Space: The set of all possible outcomes in an experiment.
  • Outcome: A single result of an experiment.

 

1.3 Probability Scale

Probability is always expressed as a number between 0 and 1:

  • 0: Impossible event
  • 1: Certain event
  • Values between 0 and 1: Varying degrees of likelihood

 

You can also express probability as a percentage (0% to 100%) or as odds (e.g., 1:3).

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