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# Statistical analysis: standard deviation

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1. A researcher is interested in estimating the noise levels in decibels at area urban hospitals. She wants to be 90% confident that her estimate is correct. If the standard deviation is 4.13, how large a sample is needed to get the desired information to be accurate within 0.68 decibels?

2. Assume that the population of heights of male college students is approximately normally distributed with mean m of 73.63 inches and standard deviation s of 6.73 inches. A random sample of 97 heights is obtained.
(a) Find the mean and standard error of the x bar distribution
(b) Find P(x bar > 73.50)

https://brainmass.com/statistics/quantative-analysis-of-data/statistical-analysis-standard-deviation-528154

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1. A researcher is interested in estimating the noise levels in decibels at area urban hospitals. She wants to be 90% confident that her estimate is correct. If the standard deviation is 4.13, how large a sample is needed to get the desired information to be accurate within 0.68 decibels? Show all work.