## Essentials of Statistics (5th Edition)

The best point estimate is equal to the proportion of the sample (x) divided by the sample size: $\hat{p}=\frac{x}{n}=0.208.$ $E=z_{\frac{\alpha}{2}}\cdot \sqrt{\frac{\hat{p}\cdot (1-\hat{p})}{n}}=1.96\cdot \sqrt{\frac{0.208\cdot (1-0.208)}{144}}=0.066.$ Confidence interval: p is between 0.208-0.066=0.142=14.2% and 0.208+0.066=0.274=27.4%.