WK 4(1)

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American Public University *

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Statistics

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Apr 26, 2024

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Week 4 Knowledge Check Homework Practice Questions - Re… Attempt 1 of 4 Written Mar 28, 2024 2:18 AM - Mar 28, 2024 4:22 AM Attempt Score 17 / 20 - 85 % Overall Grade (Highest Attempt) 17 / 20 - 85 % Question 1 1 / 1 point ___ 264.43___ Hide ques±on 1 feedback Question 2 0 / 1 point ___ 90.46___ (183.54) Hide ques±on 2 feedback The length of a human pregnancy is normally distributed with a mean of 272 days with a standard deviation of 9 days (Bhat & Kushtagi, 2006). How many days would a pregnancy last for the shortest 20%? Round answer to 2 decimal places. Answer: In Excel, =NORM.INV(0.2,272,9) The mean yearly rainfall in Sydney, Australia, is about 137 mm and the standard deviation is about 69 mm ("Annual maximums of," 2013). Assume rainfall is normally distributed. How many yearly mm of rainfall would there be in the top 25%? Round answer to 2 decimal places. Answer: Top 25% is the bottom 75%. 1 - .25 = .75. In Excel,

Question 3 1 / 1 point ___ .9987___ Hide ques±on 3 feedback Question 4 1 / 1 point Find the probability that falls in the shaded area. =NORM.INV(0.75,137,69) Find P(Z ≤ 3). Round answer to 4 decimal places. Answer: In Excel, =NORM.S.DIST(3,TRUE) 0.438 0.50 0.40

Hide ques±on 4 feedback Question 5 0 / 1 point The manufacturer of a new compact car claims the miles per gallon (mpg) for the gasoline consumption is mound-shaped and symmetric with a mean of 24.6 mpg and a standard deviation of 9.5 mpg. If 30 such cars are tested, what is the probability the average mpg achieved by these 30 cars will be greater than 28? Answer: ___ Round your answer to 4 decimal places as necessary. For example, 0.1357 would be a legitimate entry. Make sure you include the 0 before the decimal. ___ Answer: 0.3594 (0.0250) Hide ques±on 5 feedback Question 6 1 / 1 point ___ .4647___ Hide ques±on 6 feedback 0.125 (1/30)(16 - 4) This is a sampling distribution problem with μ = 24.6. σ = 9.5, and sample size n = 30. New SD = 9.5/SQRT(30) = 1.734454765 P(x > 28) = 1 – NORM.DIST(28, 24.6,1.734454765 , TRUE) The life of an electric component has an exponential distribution with a mean of 8 years. What is the probability that a randomly selected one such component has a life less than 5 years? Answer: (round to 4 decimal places) P(x < 5)

Question 7 1 / 1 point Suppose that the longevity of a light bulb is exponential with a mean lifetime of eight years. Find the probability that a light bulb lasts less than one year. Hide ques±on 7 feedback Question 8 1 / 1 point Suppose that the longevity of a light bulb is exponential with a mean lifetime of eight years. Find the probability that a light bulb lasts between six and ten years. In Excel, =EXPON.DIST(5,1/8,TRUE) 0.1175 0.1859 9.6318 0.3034 0.3682 P(x < 1) In Excel, =EXPON.DIST(1,1/8,TRUE) 0.1175 0.1859 9.6318 0.3034 0.3682

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