Answer:
a. .92
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 .
The margin of error of the interval is:
The lower bound is the point estimate subtracted by the margin of error.
The upper bound is the point estimate added to the margin of error.
Point estimate:
The confidence interval is symmetric, so it is the mean between the two bounds.
In this problem:
Sample of 400, which means that
Margin of error is the estimate subtracted by the lower bound. So
We have to find z.
has a pvalue of 0.96.
This means that:
Confidence level:
So the correct answer is:
a. .92