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The useful life of a bicycle bought at Basement-mart fits a log normal distribution with a...

The useful life of a bicycle bought at Basement-mart fits a log normal distribution with a mean of 15 months and a standard deviation of 12.8 months. Suppose that 70 bicycles are randomly chosen, and let ¯¯¯ X = X ¯ = the average useful life of a bicycle bought at Basement-mart, from a sample of 70 bicycles (in months). ¯¯¯ X ˜ X ¯ ~ ( , )

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Answer #1

Given that

mean=15

Standard deviation = 12.8

n=70

n>30 large sample follows normal distibution with mean =15 and

Standard deviation = 12.8 / √70 = 1.5298

X bar ~ N(15 ,1.5298)

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