Essentials of Business Analytics 1st Edition by Jeffrey Camm,James Cochran,Michael Fry,Jeffrey Ohlmann ,David Anderson

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The results of a national survey showed that on average, adults sleep 6.9 hours per night. Suppose that the standard deviation is 1.2 hours and that the number of hours of sleep follows a bell-shaped distribution.
a. Use the empirical rule to calculate the percentage of individuals who sleep between 4.5 and 9.3 hours per day.
b. What is the z -value for an adult who sleeps 8 hours per night
c. What is the z -value for an adult who sleeps 6 hours per night