Answer:
The 95% confidence interval on the true proportion of helmets of this type that would show damage from this test is (0.169, 0.397).
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 .
For this problem, we have that:
95% 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 95% confidence interval on the true proportion of helmets of this type that would show damage from this test is (0.169, 0.397).