How Do You Calculate Confidence Intervals for Route Preferences?

[nickelanddimed]

Consider a survey of n people asking whether they plan to use Route A or Route B, with an anticipated fraction p choosing Route A.

If p = .30, plot the 95% confidence bounds and the expected value of X as a function of n, for n = 50 to n = 800.

I have no idea where to start or how to work it out..can someone please guide me through the problem.

 

[HallsofIvy]

I have difficulty believing you have no idea! Have you been sleeping through class?

Strictly speaking, this is a "binomial distribution" problem but with n= 50 to 800, I suspect you are intended to use the Normal distribution approximation.

If p= 0.7, do you know what the mean (expected value) is for given n? Do you know how to find the standard deviation?