Question 1145302
<b>(a) Use the empirical rule to calculate the percentage of individuals who sleep between 3.9 and 9.1 hours per day.
Enter your answer as a percentage.</b>
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3.9 hours and 9.1 hours are exactly two standard deviations below/above the mean.  (One standard deviation is 1.3, so two standard deviations are 2.6.  The mean is 6.5, and 2.6 below the mean is 3.9, and 2.6 above the mean is 9.1.)  Using the empirical rule, that means 95% of individuals sleep between 3.9 hours and 9.1 per day.
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<b>(b) What is the z-value for an adult who sleeps 8 hours per night?</b>
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{{{(8-6.5)/1.3}}} = {{{1.5/1.3}}} = +1.15
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<b>(c) What is the z-value for an adult who sleeps 6 hours per night?</b>
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{{{(6-6.5)/1.3}}} = {{{(-0.5)/1.3}}} = -0.38