If a population has standard deviation 18, what is the minimum sample size to be 95% confident that the error should be accurate to within 4?
A) 153
B) 9
C) 78
D) 18

Question

Quizplus · Accepted Answer

The formula to estimate sample size when population standard deviation is known is:
n = (Zα/2 * σ / E)^2
Where:
Zα/2 = 1.96 (for 95% confidence level)
σ = population standard deviation = 18
E = margin of error = 4
Substituting the above values, we get:
n = (1.96*18/4)^2
n = 78.03
Rounding up to the nearest whole number, the minimum sample size required is 78. Therefore, the best choice is C.

If a Population Has Standard Deviation 18, What Is the Minimum