Question

Use the Empirical Rule. The mean speed of a sample of vehicles along a stretch of highway is 70 miles per​ hour, with a standard deviation of 3 miles per hour. Estimate the percent of vehicles whose speeds are between 64 miles per hour and 76 miles per hour.​

Answer 1

The Empirical Rule states that for a normal distribution, approximately 68% of the data falls within one standard deviation of the mean, approximately 95% of the data falls within two standard deviations of the mean, and approximately 99.7% of the data falls within three standard deviations of the mean.

In this case, the mean speed is 70 mph and the standard deviation is 3 mph. So, we can estimate the percent of vehicles whose speeds are between 64 mph and 76 mph as follows:

64 mph = 70 mph - 3 mph * 1

76 mph = 70 mph + 3 mph * 1

Since the speeds are within one standard deviation of the mean, we can use the Empirical Rule to estimate that approximately 68% of the vehicles have speeds between 64 mph and 76 mph.

So, the answer is approximately 68%.