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Final Exam (EC315)

# Final Exam (EC315) - PART I HYPOTHESIS TESTING PROBLEM 1 A...

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PART I. HYPOTHESIS TESTING PROBLEM 1 A certain brand of fluorescent light tube was advertised as having an effective life span before burning out of 4000 hours. A random sample of 84 bulbs was burned out with a mean illumination life span of 1870 hours and with a sample standard deviation of 90 hours. Construct a 95 confidence interval based on this sample and be sure to interpret this interval. Answer Since population standard deviation is unknown, t distribution can be used construct the confidence interval. The 95% confidence interval is given by /2, 1 /2, 1 , n n S S X t X t n n Details Confidence Interval Estimate for the Mean Data Sample Standard Deviation 90 Sample Mean 1870 Sample Size 84 Confidence Level 95% Intermediate Calculations Standard Error of the Mean 9.819805061 Degrees of Freedom 83 t Value 1.988959743 Interval Half Width 19.53119695 Confidence Interval Interval Lower Limit 1850.47 Interval Upper Limit 1889.53

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