posted by mona .
Suppose a random sample of 36 is selected from a population with a standard deviation of 12. If the sample mean is 98, the 99% confidence interval to estimate the population mean is
CI99 = mean + or - 2.58(sd/√n)
...where + or - 2.58 represents the 99% confidence interval using a z-table, sd = standard deviation, √ = square root, and n = sample size.
Substitute what you know into the above formula and go from there.
I hope this will help get you started.