PS_5 - 06April2011 PS#5 Question 1 A random sample of 12...

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06 April 2011 IE 256 STATISTICS FOR INDUSTRIAL ENGINEERS PS # 5 Question 1) A random sample of 12 shearing pins are taken in a study of the Rockwell hardness of the head on the pin. Measurements on the Rockwell hardness were made for each of the 12, yielding an average value of 48,5. Assume that the measurements are normally distributed. Assume population standard deviation is known as ߪ ൌ , 1 2 1 5 ൌ 25 ߪ ൌ 5 ҧ ൌ 80 ൌ 36 ߪ ൌ 3, ݔ ҧ ൌ 75. Question 3) In a random sample of 1000 homes in a certain city, it is found that 228 are heated by oil. (a) We believe that the sample mean is greater than population mean. Construct a 90% confidence interval for the population mean. (b) We have no intuition about the population mean. Construct a 90% confidence interval for the population mean. (c) What is the maximum size of the error related with the confidence interval?
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