Question

If I wanted the margin of error for the 95% confidence interval to be 1 inch, I should select a simple random sample of size: (assume the population standard deviation = 2.415)
A. 5.
B. 7.
C. 23.
D. 39

Answer 1

We are given with
Confidence interval of 95%. This corresponds to a Z value of 1.96
Margin of error, d = 1 inch
Population standard deviation, σ = 2.415 inch

We can calculate for the sample size using the formula
n = Z² σ² / d²
Substituting,
n = 1.96² (2.415)² / 1²
n = 22.4 ~ 23