1. The problem statement, all variables and given/known data 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? 3. 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?