- #1
toothpaste666
- 516
- 20
Homework Statement
An investigator, interested in estimating a population mean, wants to be sure that the length of the 95% confidence interval does not exceed 5. What sample size should she use if σ = 18?
The Attempt at a Solution
the formula I found in my book is n = [(z_(α/2) σ)/E]^2
z_(α/2) = z.025 = 1.96
I am fairly certain if the length of the interval can't exceed 5, then 5 will be the max error so
E = 5
n = [1.96(18)/5]^2 = 49.8
Am I doing this correctly?