In: Statistics and Probability
An environmentalist wants to find out the fraction of oil tankers that have spills each month. Step 2 of 2 : Suppose a sample of 669 tankers is drawn. Of these ships, 529 did not have spills. Using the data, construct the 98% confidence interval for the population proportion of oil tankers that have spills each month. Round your answers to three decimal places. previous answer is .209.
Solution :
Given that,
n = 669
x = 669 - 529 = 140
Point estimate = sample proportion =
= x / n = 140 / 669 = 0.209
At 98% confidence level
Margin of error = E = Z
/ 2 *
((
* (1 -
)) / n)
= 2.326 (((0.209
* 0.791) / 669)
= 0.037
A 98% confidence interval for population proportion p is ,
= 0.209 ± 0.037
= ( 0.172, 0.246 )