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Probability Calculates the likelihood an event will occur Must lie between 0 and 1 “ 0 ” implies that the event will not occur “ 1 ” implies that the event will definitely occur . Probability of an Event: P(A). Sample Space: The set of all possible outcomes of an experiment
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Probability Calculates the likelihood an event will occur • Must lie between 0 and 1 • “0” implies that the event will not occur • “1” implies that the event will definitely occur
Sample Space: The set of all possible outcomes of an experiment Example:You are rolling two dice, what is the sample space?
Sample Space: The set of all possible outcomes of an experiment Example:picking a card, what is the sample space? • 52 cards • 13 cards in each suits • 12 face cards • 4 suits:
Example • What is the probability of each of the events occurring when rolling two dice? 1) P(they add up to 2) = ? • P(2) = 1/36 2) P(6) = ? • P(6) = 5/36 3) P(10) = ? • P(10) = 3/36
Independent Events: the occurrence of one does not affect the probability of the other
Multiplication Rule Finding the probability of more than one event. The word “AND” is always used when describing the situation. 1) P(rolling a 4 and then a 2) = 1/6 *1/6 = 2.8% 2) P(rolling three odd numbers in a row) = 3/6*3/6*3/6=12.5%
Multiplication Rule for Independent Events P(A and B) = P(A) * P(B) Example: What is the probability of rolling five 6’s in a row on a six sided die. P(6&6&6&6&6) = (1/6) (1/6) (1/6) (1/6) (1/6)= 0.0001
Multiplication Rule for Independent Events P(pink and pink) = (5/11)*(5/11) = 25/121 = 21% P(A and B) = P(A) * P(B) Example: There are 11 marbles in a bag. 2 yellow, 5 pink, 4 green You pull out one marble and put it back in the bag and then pull out another marble. What is the probability of picking pink twice in a row
What is the probability of getting heads on a coin flip AND picking a brown ball out of a bag?P(heads and blue ball) Option #1: Multiply the probability of heads and brown ball: 1/3*1/2 Option #2: find the size of the sample space count the outcome of interest Use results from a and b to find the probability
Complement: P(A') = 1 - P(A) If A is an event within the sample space S of an activity or experiment, thecomplement of A (denoted A') consists of all outcomes in S that are not in A. The complement of A is everything else in the problem that is NOT in A.