Question

Engineers must consider the breadths of male heads when designing helmets. The company researchers have determined that the population of potential clientele have head breadths that are Normally distributed with a mean of 5.9 inches and a standard deviation of 0.8 inches.

According to the 68-95-99.7 rule, we expect 95% of head breadths to be
between blank and blank inches.

Answer 1

We expect 95% of head breadths to be between 4.3 inches and 7.5 inches.

Explanation:

The Empirical Rule states that, for a normally distributed random variable:

Approximately 68% of the measures are within 1 standard deviation of the mean.

Approximately 95% of the measures are within 2 standard deviations of the mean.

Approximately 99.7% of the measures are within 3 standard deviations of the mean.

In this problem, we have that:

Mean = 5.9 inches, standard deviation = 0.8 inches.

We expect 95% of head breadths to be between

Within 2 standard deviations of the mean, so:

5.9 - 2*0.8 = 5.9 - 1.6 = 4.3 inches

5.9 + 2*0.8 = 5.9 + 1.6 = 7.5 inches

We expect 95% of head breadths to be between 4.3 inches and 7.5 inches.