ProbabilityWhat is it Probability is a value ranging

Probability…What is it? Probability is a value ranging from 0 to 1 that expresses the likelihood of an event happening. P(event) = successful outcomes Possible outcomes Can be expressed as a fraction, a percent or a decimal.

Certain event • Has a probability of 1. Ex: What is the probability that you will come to school today?

Impossible event • An event that has a probability of zero. • Ex. What is the probability that you will not come to school today

Likely event • An event that has a probability greater than ½. Example: On a die, what is the probability of getting a number > 1?

Unlikely event • An event with a probability less than ½. • Ex: On a die, the chance of getting a number less than 2.

Equally likely events • Events that have an equal chance of happening. • In a deck of cards, the probability of picking the King of spades of the ace of hearts.

Experiment • An activity in which results are observed.

trial • Each observation in an experiment

Outcome • Each result in an experiment

Sample Space • The list of all possible outcomes. • For example, if you toss a coin, the possible outcomes are: • Heads (H) or Tails (T)

Event • Any set of one or more outcomes

Complementary probabilities • Probabilities which represent the whole sample space. • Example…tossing a coin • P(H) and P(T) = entire sample space • These probabilities add to 1.