The question is this:

A medical researcher claims that at least 23% of U.S. adults are smokers. In a random sample of 200 U.S. adults, 22.5% say that they are smokers. At the .01 level of significance, is there enough evidence to reject the researcher's claim?

I found .0297 to be the standard deviation. Hope that is right.

I drew the diagram with .23 as the mean and I was trying to find the critical value by going .23 + Z(.0297) I could not decide if that was the right equation and I did not know how to determine the Z that I need to use.

Any assistance on this would be wonderful. I am so lost on this one.

Thank you.