3.

On weeknights, the average number of hours of sleep per night for adults 55-84 years old is 7.0. Assume this random variable follows a normal distribution with a standard deviation of 1.1 hours.

a. What is the probability that a randomly selected adult from this age group will get 1. more than 6.0 hours of sleep tonight? 2. fewer than 5.0 hours of sleep tonight? 3. between 6.3 and 8.0 hours of sleep tonight? 4. between 5.6 and 6.5 hours of sleep tonight? b. Use Excel to confirm the answers in part a. c. How many hours of sleep will an adult in this age group get if they are in the 35th percentile?

4.

TomTom, the producer of GPS devices, reported that the fastest drivers in the nation are in Mississippi. In Mississippi, interstate drivers average 70.1 miles per hour. Assume that the speed of cars traveling on Mississippi's interstates follows the normal distribution with a standard deviation of 7.2 miles per hour. a. What is the probability that a randomly selected car on a Mississippi interstate is traveling 1. faster than 65 miles per hour? 2. slower than 72 miles per hour? 3. between 60 and 66 miles per hour? 4. between 78 and 85 miles per hour? b. Confirm the answers to part a with Excel. c. What average speed should I drive if I want to travel faster than 70% of the cars on the interstate?

5.

In a recent USA Today article titled Consumers Are Caught in a Sugar Battle, Americans consume an average of 22.2 teaspoons of sugar per day. Assume daily sugar consumption follows the normal distribution with a standard deviation of 6.5 teaspoons. a. What is the probability that a randomly selected American will consume 1. more than 25 teaspoons of sugar today? 2. between 20 and 27 teaspoons of sugar today? 3. between 10 and 18 teaspoons of sugar today? 4. between 28 and 35 teaspoons of sugar today? b. Confirm the answers to part a with Excel. c. How many teaspoons of sugar will a person consume today if he or she is in the 65th percentile?

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