Answer:
The 80% confidence interval for the population proportion of oil tankers that have spills each month is (0.199, 0.257).
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of , and a confidence level of
, we have the following confidence interval of proportions.
In which
z is the zscore that has a pvalue of .
Suppose a sample of 333 tankers is drawn. Of these ships, 257 did not have spills.
333 - 257 = 76 have spills.
This means that
80% confidence level
So , z is the value of Z that has a pvalue of
, so
.
The lower limit of this interval is:
The upper limit of this interval is:
The 80% confidence interval for the population proportion of oil tankers that have spills each month is (0.199, 0.257).