STAT10x9.20.05Probability2 - Probability in Practice(The...

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Probability in Practice (The trick is knowing when to apply which probability rule!) Suggestions : Read the Textbook. I like it. Do problems in book. They have solutions. Make a picture. This helps to clarify sample spaces. Do some more problems. Example : An Entertainment Weekly poll taken over the weekend showed that people’s choice for Emmy for best drama was (voters could pick only one show) Lost 44% Six Feet Under 17% 24(?) 18% The West Wing 11% Suggestion : Check to see if probabilities satisfy requirements : Let A be the event that a person likes a particular show above. 1) For any event A , 1 ) ( 0 A P (all fine here) 2) 1 ) ( = S P (umm . . .) STAT 101-106 Introduction to Statistics 117
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Probabilities of events so far only add to 90%, so make a new category called ‘Other’ and assign it a probability of 10%. Question : what is the probability that a person picked at random would list ‘24’ or ‘The West Wing’ as best drama? Help : ‘or’ means P(A or B) . Use addition rule and then think about whether events are disjoint. P(24 or WestW) = P(24) + P(WestW)–P(24 and Westw) Last probability is zero since can’t have two favorite shows – i.e., these events are disjoint : P(24 and Westw)= 0. So : P(24 or WestW) = P(24) + P(WestW) = .18 + .11 = .29 Question : what is the probability that three randomly chosen people all pick “24” as their favorite show?
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STAT10x9.20.05Probability2 - Probability in Practice(The...

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