The [tex] (1-\alpha )100\% [/tex] confidence interval for proportion is
[tex] p \pm z_{\alpha /2} \sqrt{\frac{p(1-p)}{n}} [/tex]
Here [tex] p=\frac{55}{100}=0.55,\alpha =0.01 [/tex]
Using standard normal tables [tex] z_{\alpha /2}=-2.576 [/tex].
The 99% confidence interval for proportion is
[tex] 0.55 \pm 2.576\sqrt{\frac{0.55(1-0.55)}{100}} [/tex]
[tex] (0.422,0.678) [/tex]
The CI interpretation is that "We are 99% confident that the proportion of voters in favor of the candidate lies between 0.422 and 0.678".
