Standard Deviation

Question

Terri Vogel, an amateur motorcycle racer, averages 129.71 seconds per 2.5 mile lap (in a 7 lap race) with a standard deviation of 2.28 seconds. The distribution of her race times is normally distributed. We are interested in one of her randomly selected laps.

Find the percent of her laps that are completed in less than 132 seconds. (Round your answer to two decimal places.)

Answer 1

P(X<132) = P(Z<[132-129.71]/2.28) = P(Z<1) = 0.8413 = 84.13%

P(Z<1) can easily be determined by the Empirical Rule

Hope this helped!