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Tutorial 6

Tutorial 6 - THE UNIVERSITY OF HONG KONG DEPARTMENT OF...

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3. The net weight of packages of beef sold in a supermarket are labeled "3 pounds." A complaint has been made 2. A company wants to estimate the 99% confidence interval for the lifetime of inkjet printer heads produced. The 1. 225 flight records are randomly selected, giving a sample mean of 11.6 unoccupied seats. Given that the population Example Class 6 1 THE UNIVERSITY OF HONG KONG DEPARTMENT OF STATISTICS AND ACTUARIAL SCIENCE STAT0302 Business Statistics (Semester 2, 2012/2013) Questions Confidence Interval Given X N ( μ, σ 2 ) , where the population mean μ is unknown and the population variance σ 2 is known. The (1 α )% confidence interval estimate for μ is given by ¯ x z α 2 σ n , ¯ x + z α 2 σ n where ¯ x is the sample mean of a sample with size n drawn from the population and P ( Z > z α 2 ) = α 2 Determining the sample size The margin of error is given by half the length of a confidence interval. Suppose we require the margin of error not to be more than a number E at the (1 α )% confidence interval, we need a sample of size n such that n z α 2 σ E 2 standard deviation of unoccupied seats in a flight is σ = 4.1 seats, estimate a 95% confidence interval for the

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