Question

Of 1000 randomly selected cases of lung cancer, 838 resulted in death within 10 years. Construct a 95% two-sided confidence interval on the death rate from lung cancer. (a) Construct a 95% two-sided confidence interval on the death rate from lung cancer. Round your answers to 3 decimal places. (b) Using the point estimate of p obtained from the preliminary sample, what sample size is needed to be 95% confident that the error in estimating the true value of p is less than 0.03

Answer 1

0.8152 ≤ p ≤ 0.8608

579

Explanation:

Given the following :

Samples size n = 1000

Deaths within 10 years, p = 838

α = 95%

Construction a two way confidence interval:

p ± Zα/2 * √p(1-p) / n

point estimate p = 838/n = 838/1000 = 0.838

Z0.05/2 = Z0.025 = 1.96

0.838 - 1.96√0.838(1-0.838) / 1000

0.838 - 1.96*0.0116514 = 0.8152

0.838 + 1.96√0.838(1-0.838) / 1000

0.838 + 1.96*0.0116514 = 0.8608

0.8152 ≤ p ≤ 0.8608

b) Using the point estimate of p obtained from the preliminary sample, what sample size is needed to be 95% confident that the error in estimating the true value of p is less than 0.03

Error (E) = 0.03

To find the samome size, use the relation:

n = (Zα/2 / E)² * p(1-p)

n = (1.96/0.03)² * 0.838(1-0.838)

n = (1.96/0.03)² * 0.838 * 0.162

n = 4268.4444 * 0.838 * 0.162

n = 579.46

n = 579