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stacester115 · Jul 28, 2007, 04:20 PM

Can anyone help me solve this problem?

Random security checks of 65 travelers at JFK international airport have caused an average of 17 of those travelers to be "red-flagged" for further checks. The population standard devidation is 12 red flags per day.
1. find 90% confidence interval of the true population mean of red flagged
2. find 90% " " " " " using a reduced sample of 29 people less

galactus · Jul 29, 2007, 02:19 PM

$n=65, \;\ \overline{x}=17, \;\ {\sigma}=12.$

Find 90% CI.

This isn't bad.

The margin of error is given by $E=z\cdot\frac{\sigma}{\sqrt{n}}$

A 90% CI corresponds to a z score of 1.645.

Now find the margin of error and find $\overline{x}-E$ and $\overline{x}+E$

The you will have $\overline{x}-E<{\mu}<\overline{x}+E$

Then, for part b, do the same thing with n=36