Name Confidence Interval Estimates 20 points due March 6 2014 1 A High Tech company wants to estimate the mean number of years of college education its employees have completed A good estimate of the standard deviation for the number of years of college is 1 2 How large a sample needs to be taken to estimate m within 1 2 year with 95 confidence 1 pt 2 A sample of 60 night school students had an average age of 25 3 years Use this information and a population variance of 16 to find a a 95 confidence interval estimate for the population mean 2 pts b 99 confidence interval estimate for the population mean 2 pts c Redo part a assuming 16 is the sample variance 2 pts 3 If ninety percent of the Student s t distribution lies to the right of t 1 37 what is the degrees of freedom for this distribution 1 pt 4 Use the pulse rates for a random sample of adult women listed below to determine a 90 confidence interval estimate for the population average pulse rate for all adult women Assume that pulse rate is normally distributed 2 pts 83 58 70 56 76 64 80 76 70 97 68 78 108 5 Use the data in question 4 find an 80 confidence interval estimate for the population variance in pulse rate 2 pts 6 You decide to monitor deaths caused by drugs in your community For the next 250 individuals whose deaths are drug related 123 were caused by legally prescribed drugs and the rest were the result of illicit drug use Find the 90 confidence interval for the proportion of drug related deaths that are caused by legally prescribed drugs 2pts 7 Use the information from question 6 to determine the sample size that you would need if you wanted to replicate the study with 99 confidence and a maximum error of estimate equal to 01 or 1 1 pt 8 A manufacturer of a photographic chemical wants to estimate the standard deviation of the shelf life of his product The company knows that this shelf life is normally distributed He tests a sample of 14 jars of his product The average shelf life is 180 days with a standard deviation of 12 days Use this data to find a a 90 confidence interval estimate for the standard deviation of shelf life for this product 2 pts b 95 confidence interval estimate for the variance of the shelf life of this product 1 pts c 90 confidence interval estimate for the mean shelf life of this product 2 pts
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