chpt7

# chpt7 - A Couple Less-obvious Chapter 7 questions 1 A ski...

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A Couple Less-obvious Chapter 7 questions 1) A ski lift is designed with a load limit of 18,000 pounds. It claims to have a capacity of 100 people. Suppose the weights of all the people using the life have a mean of 175 pounds and a standard deviation of 30 pounds. What is the probability that a random group of 100 people will total more than the load limit of 18,000 pounds? Ans: Let X 1 represent the weight of the first person on the ski lift, X 2 the weight of the second person, etc. The question is ( 29 100 1 100 1 1800 0? 18000 ? 10 0 100 18 i i i i PX X P = =  =   = = ( 29 ( 29 175 30 3 10 18 0 175 1.6 7 1.6 7 .0475 3 X EX n z Pz m s s == = == - = 2) The managers of Mercury Mufflers find that the time t (in minutes) required for a worker to replace a muffler varies. Over a period of a year, they collected the following data: t Relative Frequency 20 10% 30 50% 40 30% 50 10% a) Calculate the mean and standard deviation of t. ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 ( 29 2 2222 20 . 1 30 . 5 40 . 3 50 . 1 34 2 0 3 4 . 1 3 0 3 4 . 5 4 0 3 4 . 3 5 0 3 4 .1 6 48 x x fx x m sm = =+++= =- + - + - +-

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chpt7 - A Couple Less-obvious Chapter 7 questions 1 A ski...

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