Question

# Terri Vogel, an amateur motorcycle racer, averages 129.73 seconds per 2.5 mile lap (in a 7...

Terri Vogel, an amateur motorcycle racer, averages 129.73 seconds per 2.5 mile lap (in a 7 lap race) with a standard deviation of 2.25 seconds . The distribution of her race times is normally distributed. We are interested in one of her randomly selected laps. (Source: log book of Terri Vogel) Let X be the number of seconds for a randomly selected lap. Round all answers to 4 decimal places where possible.

a. What is the distribution of X? X ~ N(___,___)

b. Find the proportion of her laps that are completed between 129.38 and 131.04 seconds. ____

c. The fastest 4% of laps are under ____ seconds.

d. The middle 60% of her laps are from ____ seconds to ____ seconds.

a)X ~ N(129.73 , 2.25)

b)

 for normal distribution z score =(X-μ)/σx here mean=       μ= 129.73 std deviation   =σ= 2.2500
 probability = P(129.38

c)

 for 4th percentile critical value of z= -1.75 therefore corresponding value=mean+z*std deviation= 125.79 seconds

d)

The middle 60% of her laps are from _127.84_ seconds to _131.62_ seconds

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