In one day, a random security check of 65 travelers at JFK
international airport would cause 17 of those travelers to be “red-flagged” for
further checks. The
population standard deviation (nation wide) is 12 “red-flags” per day.
Using the JFK sample, find the 90%
confidence interval of the true population mean of the number
of people “red-flagged.”
You'll need to use a different kind of formula for these proportional problems.
Here is one:
CI90 = p + or - (z-value)(√ pq/n)
Find z-value using a z-table representing 90%. p = 17/65 (convert to a decimal). q = 1 - p. n = 65 (sample size). Plug values into the formula and calculate the interval.
I hope this will help get you started.