Answer:
The 90% confidence interval for the percentage of people the company contacts who may buy something is between 10.82% and 14%
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:
90% 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 90% confidence interval for the percentage of people the company contacts who may buy something is between 10.82% and 14%