Question

The mean hours of sleep that students get per night is 7 hours, the standard deviation of hours of sleep is 1.7 hours, and the distribution is approximately normal. Complete the following sentence. For about 95% of students, nightly amount of sleep is between ______.a. 5.3 and 8.7 hrsb. 5 and 9 hrsc. 3.6 and 10.4 hrsd. 1.9 and 12.1 hrs

Answer 1

c. 3.6 and 10.4 hrs

Explanation:

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

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

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

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

In this problem, we have that:

Mean 7, standard deviation 1.7.

For about 95% of students, nightly amount of sleep is between

7 - 2*1.7 = 7 - 3.4 = 3.6 hours

7 + 2*1.7 = 7 + 3.4 = 10.4 hours

So the correct answer is:

c. 3.6 and 10.4 hrs