Only 200 of the 1500 people you survey like a new flavor of

Only 200 of the 1500 people you survey like a new flavor of Snapple (Crazy Tofu Berry). Construct the 95% Confidence Interval for the true population proportion that like this new Snapple flavor. Report the UPPER confidence interval value as 0.XX Assume the statistical value you need is 1.96

Solution

p=200/1500 = 0.1333333

So the 95% Confidence Interval is

p +/- Z*sqrt(p*(1-p)/n)

--> 0.1333333 +/- 1.96*sqrt(0.1333333*(1-0.1333333)/1500)

--> (0.1161302, 0.1505364)

So the UPPER confidence interval value is 0.1505364