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A safety officer wants to prove that the average speed of cars driven by a school...

A safety officer wants to prove that the average speed of cars driven by a school is less than 25 mph. Suppose that a random sample of 14 cars shows an average speed of 24.0 mph, with a sample standard deviation of 2.2 mph. Assume that the speeds of cars are normally distributed.

Provide the notation for the underlined value. That is, what does it represent?

Math   Statistics-And-Probability   
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Answer #1

Solution :

= / n = 2.2 / 14 = 0.5880

P( < 25) = P(( - ) / < (25 - 24.0) / 0.5880)   

P(z < 1.70)

= 0.9554

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