Please help! A sample of 5 months, an average of 28 mail carriers were bitten by dogs each month. The standard deviation of the sample was 3. Find the 90% confidence interval of the true mean number of mail carriers who are bitten by dogs each month. Assume the variable is normally distributed.

Question

Please help!  A sample of 5 months, an average of 28 mail carriers were bitten by dogs each month.  The standard deviation of the sample was 3.  Find the 90% confidence interval of the true mean number of mail carriers who are bitten by dogs each month.  Assume the variable is normally distributed.

amistre64 · Answer

I believe its something like:
$$\bar X\pm Z_{90\%}\sqrt{\frac{\sigma^2}{n}}$$

anonymous · Answer

What is the Z?