Posted by **Joe** on Wednesday, September 30, 2009 at 8:37pm.

A simple random sample of 25 has been collected from a normally distributed population for which it is know that o=17.0. The sample mean has been calculated as 342.0, and the sample standard deviation is s=14.9. Construct and interpret the 95% and 99% confidence intervals for the population mean.

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**MathGuru**, Thursday, October 1, 2009 at 10:44am
CI95 = mean + or - 1.96(sd divided by √n)

...where + or - 1.96 represents the 95% confidence interval using a z-table, sd = standard deviation, √ = square root, and n = sample size.

For the 99% confidence interval, you will have to substitute the value from a z-table that corresponds to 99%.

Put the values you are given from the problem into the formula and go from there to determine your confidence intervals.

I hope this will help get you started.

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