Find a 99% confidence interval for the population mean for a sample of size 36 that yields a mean of 78 and a standard deviation of 6. Assume sigma, the population standard deviation, is unknown.

A) (74.2, 81.8) B) (76.00, 80.03) C) (75.28, 80.72) D) None of the above

  • $\begingroup$ What have you tried? You are intended (though it is not stated) to assume a normal distribution. You should have a formula for the variance of the mean of a sample. $\endgroup$ – Ross Millikan Apr 8 '14 at 2:31
  • $\begingroup$ No.${}{}{}{}{}$ $\endgroup$ – user98602 Apr 8 '14 at 2:33

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