Continuing the exam-score example, σ = 3, n = 36, x-bar = 68, and z(0.05) = 1.645 for a 90% confidence level. What is the resulting confidence interval?

1. Compute EBM = z(σ/sqrt(n)) = (1.645)(3/sqrt(36)) = (1.645)(0.5) = 0.8225. 2. Lower bound: 68 - 0.8225 = 67.1775, which rounds to 67.18. 3. Upper bound: 68 + 0.8225 = 68.8225, which rounds to 68.82. 4. Option D doubles the error bound by mistake, giving a needlessly wide interval. _Source: OpenStax Introductory Statistics (CC BY 4.0), Ch 8 "Confidence Intervals", section 8.1 A Single Population Mean using the Normal Distribution_