Question

Trials in an experiment with a polygraph include 97 results that include 23 cases of wrong results and 74 cases of correct results. Use a 0.05 signifcance level to test the claim that such polygraph results are correct less than 80% of the time. Based on the results should polygraph test results be prohibited as evidence in trials? identify the null hypothesis, alternative hypothesis, test statistic, P-value conclusion about the null hypothesis and final conclusion that addresses the original claim. Use the P-value method. Use the normal distribution as an approximation of the binomial distribution

a. H0:p= 0.80 b. H0:p=0.20
H1:p>0.80 H1: p =/ 0.20
c. H0:p=0.20 d. H0:p= 0.80
H1:p< 0.20 H1: p< 0.80
e. H0: p= 0.20 f. H0: p= 0.80
H1: p>0.20 H1:p =/ 0.80
the test statistic is z=
the P-value is ?

Answer 1

H0:p= 0.80 H1: p< 0.80 one tailed test

Explanation:

We state the null and alternative hypotheses as that the results are 80 % against the claim that the results are less than 80%.

H0:p= 0.80 H1: p< 0.80 one tailed test

p2= 0.8 , p1= 74/97= 0.763

q1= 1-0.763= 0.237 q2= 0.2

The level of significance is 0.05 .

The Z∝= ±1.645 for ∝= 0.05

The test statistic used here is

Z= p1-p2/ √pq/n

Putting the values:

Z= 0.763 -0.8 / √ 0.8*0.2/97

z= -0.037/ 0.0406

z= -0.9113

The Z∝ = ±1.645 for ∝= 0.05 for one tailed test.

As the calculated value does not fall in the critical region we fail to reject the null hypothesis. There is not sufficient evidence to support the claim that such polygraph results are correct less than 80% of the time.

Using the normal probability table.

P (Z < -0.9113)= 1- P(z= 0.9311) = 1- 0.8238= 0.1762

If P- value is smaller than the significance level reject H0.

0.1762> 0.005 Fail to reject H0.