I am having trouble with one of my questions it goes:

It is claimed that fewer than 30% of Thunder Bay households have home delivery of the newspaper. To test this claim, a random sample of 390 Thunder Bay households reveals that only 95 get the paper delivered. Using an alpha value of 0.01, what conclusion can be reached about the claim? (Test Statistic z* or t*)

H0: P=0.3

H1: P not equal to 0.3

I am pretty sure I am doing t* because the sample size is greater than 30, but the formula we are to us is x-Mu/S/sqrt(n)

x=95

Mu=0.3

S=?

n=390 (I'm not sure if those are right either)

I don't know how to find the standard deviation (s) I tried using S= sqrt[(np)(1-p)] where n=390 and p=30% (0.3) but my final answer is 9.05, and when I plug it into the first formula I get a large number 206.7 and I don't think that is right.

I just don't know how to find standard deviation for this equation and what to do after I solve the equation

Thanks!