Answer:
a) The sample proportion is of 0.6.
b) The 95% confidence interval for the proportion of potential customers who prefer your product is (0.4642, 0.7358).
c) A sample size of 145 is needed.
Step-by-step explanation:
(a) Find the sample proportion.
30 out of 50. So
The sample proportion is of 0.6.
(b) Find the 95% confidence interval for the proportion of potential customers who prefer your product.
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 for the proportion of potential customers who prefer your product is (0.4642, 0.7358).
(c) If you want the 95% maximum likely error to be 0.08 or less, what would you choose for a sample size
The margin of error is:
We need a sample size of n, and n is found when M = 0.08. So
Rounding up
A sample size of 145 is needed.