Chapter 6 3.) AAA reports that the average time it takes to respond to a roadsid

Question

Chapter 6

3.) AAA reports that the average time it takes to respond to a roadside emergency is 25 minutes, with a standard deviation of 4.5 minutes. For a randomly selected sample of 5 emergency response calls what is the probability that the average wait time is less than 22 minutes for a roadside emergency? (give your answer as a rounded 4 place decimal)

4.) The average number of hours that a student spends per day working at a computer is 3.5 hours. This distribution is normally distributed with a standard deviation of 0.9 hours. What percentage of students spend more than 3.8 hours per day working at a computer? (express your answer as a decimal rounded to four decimal places)

Part II The average number of hours that a student spends per day working at a computer is 3.5 hours with a standard deviation of 0.9 hours. What is the probability that a randomly selected sample of 12 students will spend an average of more than 3.8 hours per day working on a computer? (express your answer as a decimal rounded to four decimal places)

5.) DMV reports that the average age of a vehicle in Santa Clara is 9 years old (108 months). Assume that the distribution of vehicle ages is normally distributed with a standard deviation of 18 months. What percent of vehicles in Santa Clara are between 10 (120 months) and 15 years old (180 months). (Express your answer as a decimal rounded to four decimal places)

Part II The DMV reports that the average age of a vehicle in Santa Clara is 9 years old (108 months) with a standard deviation of 18 months. For a random sample of 20 vehicles in Santa Clara what is the probability that the average age of the vehicles in the sample is between 10 (120 months) and 15 years old (180 months). Give your answer as a decimal rounded to the fourth decimal place.

Explanation / Answer

3. we know that z = ( 22 - ) / (÷) = -1.4907
P (x < 22) = P (z < -1.4907) = 0.068

4.   Zscore is (3.8-3.5)/0.9=.3333; from normal table, area to the right of .3333 is .3695.

Zscore is (3.8-3.5)/[0.9/sqrt(12)]=1.1547; from normal table, area to the right of
1.1547 is .1241.

5.

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