SOLUTION: Replacement times for TV sets has a mean of 8.2 years and a standard deviation of 1.1 years. a. What is the probability that a randomly selected TV set will have replacement

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Question 1177946: Replacement times for TV sets has a mean of 8.2 years and a standard deviation of 1.1 years.

a. What is the probability that a randomly selected TV set will have replacement time in less than 8 years? Give your answer to four decimal places.
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b. What is the probability that 40 randomly selected TV sets will have a mean replacement time that is less than 8 years? Give your answer to four decimal places.
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Answer by ewatrrr(24785) (Show Source):
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Hi Normal distribution: μ = 8.2years σ = 1.1years Using TI or similarly an inexpensive calculator like a Casio fx-115 ES plus a. P(x < 8) = normalcdf(-9999, 8,8.2,1.1) = 0.4279 b. P( x̄ < 8)= normalcdf(-9999, 8,8.2,1.1/√40) = .125 or z = (8-8.2)/1.1/sqrt(40) = -1.1499 P( z ≤ -1.1499) = .125 Wish You the Best in your Studies.