Question

A study of the amount of time it takes a mechanic to rebuild the transmission for...

A study of the amount of time it takes a mechanic to rebuild the transmission for a 2005 Chevrolet Cavalier shows that the mean is 8.4 hours and the standard

deviation is 1.8 hours. If 40 mechanics are randomly selected, find the probability that their mean rebuild time exceeds 8.7 hours.

Math   Statistics-And-Probability   
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Answer #1

Solution :

Given that ,

mean = = 8.4

standard deviation = = 1.8

n = 40

= 8.4

= / n = 1.8/ 40 =0.2846

P( >8.7 ) = 1 - P( <8.7 )

= 1 - P[( - ) / < (8.7-8.4) / 0.2846 ]

= 1 - P(z < 1.05)

Using z table

= 1 - 0.8531

= 0.1469

probability= 0.1469

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