SOLUTION: If anyone can help me answering this question would be greatly appreciated The speed of all cars traveling on a highway is normally distributed with a mean of 68 miles per hour

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Question 871457: If anyone can help me answering this question would be greatly appreciated
The speed of all cars traveling on a highway is normally distributed with a mean of 68 miles per hour and a standard deviation of 3 miles per hour. Find the probability that the mean speed of random sample of 16 cars traveling on the highway is:
a) less than 66mph
b) more than 69mph
c) between 67 and 69mph
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!


Hi

m = 68mph, SD = 3,  s = 3/sqrt(16) = 3/4

sample 16 

a) P(xbar < 66mph), z = -2/(3/4) = -8/3 = -2.6667

P(z < -2.6667) = .0038   0r  .38%

b)P(xbar > 69mph), z = 1/(3/4) = 4/3

P(z > 1.3333) = .0912   0r 9.12%

P( 67 < xbar <69 ) = .9088 - .0912 = .8976   0r 89.76%

0r P( 67 < xbar <69 )= normalcdf(67, 69, 68, .75)