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2 answers:
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Answer:
The 95% confidence interval for the true proportion of all voters in the state who favor approval is (0.4384, 0.5050).
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 for the true proportion of all voters in the state who favor approval is (0.4384, 0.5050).
Answer:
a. Grand Mean = 2.799
b. Standard Deviation = 0.01387
c. Standard Error = 0.0016
d. The range with a Z score of 3 = (2.75739, 2.84061)
Step-by-step explanation:
a. Grand mean :
Given that
Sum of 80 values = 223.91
Total observation = 80
Grand mean = 223.91/80 = 2.799
b. With the excel command "STDEV[range of cells]", we get the standard deviation as = 0.01387
c. Standard error = Standard deviation / root of n
d. The range with a Z score of 3 :
lower limit = mean - (3 * SD) = 2.799 - (0.04161) = 2.75739
upper limit = mean + (3 * SD) = 2.799 + (0.04161) = 2.84061