An environmentalist wants to find out the fraction of oil tankers that have spills each month. Step 2 of 2 : Suppose a sample of 432 tankers is drawn. Of these ships, 337 did not have spills. Using the data, construct the 85% confidence interval for the population proportion of oil tankers that have spills each month. Round your answers to three decimal places.
The sample of 432 tankers is drawn. Of these ships, 337 did not have spills, so 432-337 = 95 have spills so the proportion of spills will; be:
The confidence interval is calculated as:
the Zc is critical Z score calculated at 85% confidence level computed using excel formula =NORM.S.INV(0.925) which results in Zc = 1.4395
so, now the confidence interval for population proportion is calculated as:
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