# confidence intervals fir the population mean u

• Oct 24th 2008, 09:46 AM
diabetesman
confidence intervals fir the population mean u
Hello I'm having trouble with this problem below. What i need to do is find the indicated confidence interval for the population mean u. Can anyone help me please.

c=.95, x=31.39, s=.8, n=82

Thanks for the help in advance.
• Oct 24th 2008, 10:13 AM
galactus
There'snot much to a CI. The formula is $E=z\cdot \frac{\sigma}{\sqrt{n}}$

You have ${\sigma}$ and n, plug them in. The z score for a 95% is 1.96.

Find that value, then add and subtract it from the mean. That's it.

You should get E=about .17 if you do it right.
• Oct 24th 2008, 02:59 PM
diabetesman
ok thank you very much that makes alot more sense.