Step 1 :Identify the null hypothesis and the alternative hypothesis. The null hypothesis is that the polygraph results are correct 80% of the time, denoted as \(H_{0}: p=0.80\). The alternative hypothesis is that the polygraph results are correct less than 80% of the time, denoted as \(H_{1}: p<0.80\).
Step 2 :Calculate the test statistic using the formula for a proportion, which is \((p_{hat} - p_{0}) / \sqrt{(p_{0} * (1 - p_{0})) / n}\), where \(p_{hat}\) is the sample proportion, \(p_{0}\) is the null hypothesis proportion, and \(n\) is the sample size. In this case, \(n = 98\), \(x = 76\), and \(p_{hat} = 0.7755102040816326\), so the test statistic is approximately \(z=-0.61\).
Step 3 :Calculate the P-value, which is the probability of observing a test statistic as extreme as the one we calculated, assuming the null hypothesis is true. Using the normal distribution, the P-value is approximately \(0.27\).
Step 4 :Make a conclusion about the null hypothesis. Since the P-value is greater than the significance level of 0.01, we fail to reject the null hypothesis. This means that there is not enough evidence to support the claim that the polygraph results are correct less than 80% of the time.
Step 5 :\(\boxed{\text{Final Answer: The null hypothesis is } H_{0}: p=0.80 \text{ and the alternative hypothesis is } H_{1}: p<0.80. \text{ The test statistic is approximately } z=-0.61 \text{ and the P-value is approximately } 0.27. \text{ There is not enough evidence to reject the null hypothesis, so we cannot support the claim that the polygraph results are correct less than } 80 \% \text{ of the time.}}\)