Use the following information for following questions . A police radar gun is used to measure the speeds of cars on a
highway. The speeds of cars are normally distributed with a mean of 55 mi/hr and a standard deviation of 5
mi/hr.
-Roughly what proportion of cars are driving between 60 and 70 mi/hr? Round to the nearest thousandth)
A)0.157
B)0.843
C)0.314
D)0.628

Question

Quizplus · Accepted Answer

The z-score for 60 mi/hr is (60 - 55) / 5 = 1. The z-score for 70 mi/hr is (70 - 55) / 5 = 3. The proportion of cars driving between 60 and 70 mi/hr is the area under the normal curve between z = 1 and z = 3, which is 0.157.

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