# Lab 9.docx - Lab 9 Tutorial 1 Confidence intervals The max...

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Lab 9 / Tutorial 1: Confidence intervals The max grade for this lab is 110 but the scale is still 100 points. The 10 points are extra credit. The following video might be helpful: Confidence interval Note: numbers are truncated. There is no need to use any data to perform actual test. The actual P -value is given to you. Set-up : The manufacturer introduced a new version of a machine and it was sued for not disclosing the additional maintenance cost. The average annual maintenance cost for the older model was \$1170. Given the data for the recent machines, decide if the law suit holds water. (Need to manually input the data into Excel). What test/procedure should be run? (Click for answer) We need to compute the confidence interval (with 95% confidence) What is the margin of error? (Click for answer) We need to compute standard deviation: type = StDev(Array1) and the answer is 1097.1. After that type = Confidence.T(0.05,1097.1,12), where 12 stands for 12 data points. The answer should be 697.0661 What is the Statistical interpretation? (Click for answer)
Theory tells us that the 95% confidence interval is equal to [Average – Margin of Error, Average + margin of Error]. In our case the average is equal to 1632.833, thus the interval is [935.7673, 2329.899]. What is the conclusion? (Click for answer)
Lab 9 / Task 1 In what follows use any of the following tests/procedures: Regression, confidence intervals, one- sided t-test, or two-sided t-test. All the procedures should be done with 5% P-value or 95% confidence interval. Open Brain data. SETUP: It is believed that the larger the head circumference the larger the brain volume should be. Given the data your job is to confirm or disprove this assertion. 1. What test/procedure did you perform? Correct Answer
d. Confidence interval