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11.9 Probability Probability (chance) is a measure of how likely a certain event will occur. Proper notation: P(event) Example: P(H), means the probability of flipping heads in a coin toss Probability fraction: favorable outcomes . total possible outcomes *When asked to give “probability percent”, simply convert the above fraction to a percent. Independent Events: the outcome does not depend on another event Dependent Events: when one event affects another event Example: taking colored marbles from a bag: as you take each marble there are less marbles left in the bag, so the probabilities change. 2 or More Events Find the probability of each separate event and then multiply the events. Remember to reduce fractions! Example: (Coin Toss) Find the probability of tossing 3 heads in a row. 1 For each toss of a coin landing on “heads" has a probability of 2 nd rd 1st toss x 2 toss x 3 toss = probability 1 2 x 1 2 x 1 2 = 1 8