Statistics HW 3

# Statistics HW 3 - Question 1 0.25 out of 0.25 points...

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Question 1 0.25 out of 0.25 points Description The purpose of this homework is to practice the statistical methods given in lectures 5, 6 and 7 in addition to all previous lectures. Instructions: When you are reporting the sample sizes, the calculated end result should be rounded up to the nearest integer . Example: 99.09 should be reported as 100 and 99.99 should also be reported as 100. The answers for confidence intervals should be directly copied from the output in Minitab. Use Minitab to answer the questions. To answer the following questions, only use the given information in the question. First problem: When the power of a test is low (i.e. 1 – β = .30) then we need to: Selected Answer: increase the sample size Answers: increase the sample size decrease the sample size decrease the p-value increase the standard deviation Question 2 0.25 out of 0.25 points Suppose that the standard deviation of the difference between the two methods is σ = 12. If you want to do a test with type I error ( α = 0.01), and you want to detect a difference of Δ = 10 units, what sample size is necessary to get a power of: 50% ? Selected Answer: 1 0 Correct Answer: Evaluation Method Correct Answer Pattern Match 10 Question 3

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0.25 out of 0.25 points Suppose that the standard deviation of the difference between the two methods is σ = 12. If you want to do a test with type I error ( α = 0.01), and you want to detect a difference of Δ = 10 units, what sample size is necessary to get a power of: 80% ? Selected Answer: 1 7 Correct Answer: Evaluation Method Correct Answer Pattern Match 17 Question 4 0.25 out of 0.25 points Suppose that the standard deviation of the difference between the two methods is σ = 12. If you want to do a test with type I error ( α = 0.01), and you want to detect a difference of Δ = 10 units, what sample size is necessary to get a power of: 90% ? Selected Answer: 2 2 Correct Answer: Evaluation Method Correct Answer Pattern Match 22 Question 5 0.25 out of 0.25 points What happens to confidence intervals as sample sizes increase? Selected Answer: They get narrower Answers: Nothing They get wider They get narrower Question 6 0.25 out of 0.25 points What happens to confidence intervals as sample sizes decrease? Selected Answer: They get wider Answers: They get
narrower They get wider Nothing Question 7 0 out of 0.25 points Consider the armspan data for males (Lecture 7). The numeric answers will be calculated using Minitab. The difference between height and armspan is of interest. The sample mean of difference is -0.26 and the sample size n = 50. Suppose the population standard deviation of the difference is σ = 1.45. Compute the 99% confidence interval for the population mean of the difference. The interval is ( [a] , [b] ). Specified Answer for: a - 0.901 Specified Answer for: b 0.38 1 Correct Answers for: a Evaluation Method Correct Answer Pattern Match -0.788 Correct Answers for: b Evaluation Method Correct Answer Pattern Match 0.268 Question 8 0.25 out of 0.25 points Consider the armspan data for males (Lecture 7). The numeric answers will be calculated using Minitab. The difference between height and armspan is of interest.

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• Summer '16
• Rick Simmons

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