## anonymous one year ago In a sample of 200 households, the mean number of hours spent on social networking sites during the month of January was 55 hours. In a much larger study, the standard deviation was determined to be 7 hours. Assume the population standard deviation is the same. What is the 99% confidence interval for the mean hours devoted to social networking in January?

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1. anonymous

99% confidence level is mean $$\pm$$ 2.58 standard deviations.