Likelihood of Events





Def: Probability—the likelihood that an event will occur.




Def: Experiment—a process that when performed results in one and only one outcome.

            EX: Toss a cup—record how it lands


Def: Outcomes—the observations of an experiment.

            EX: Side, Upside-Down, Right-Side Up


Def: Sample Space—the collection of all outcomes for an experiment (denoted: S).

            EX: S = {Side, Upside-Down, Right-Side Up}


Right-side up



Def: Impossible Event—an event that absolutely cannot occur.


Def: Certain Event—an event that is guaranteed to occur (aka—sure event).











--A random event is one in which we are not sure of exactly what will happen even though we know the possible outcomes and we can predict a long-term pattern.


EX: Tossing a Coin

            We know we will either get heads or tails.  But, on any given toss we do not know        what we will get.  We expect, though, to get heads about half of the time.


Heads or Tails


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