posted by Anonymous .
In a survey randomly selected subjects, the mean age of the 36 respondents is 40.0 years and the standard deviation of the ages is 10.0 years. Use these sample results to construct a 95% confidence interval estimate of the mean age of the population from which the sample was selected.
95% confidence means that you will have 5% left in the two tails. Split this number in half to get .025 in each tail.
This is equivalent to a z-score of 1.96
Use this z-score in the formula to find the confidence interval.