A Step-by-Step Introduction to Statistics for Business
Second Edition
Chapter 6: Estimation and Confidence Intervals
Answers for Data Skill Challenges for every chapter in the book can be found to check your performance and widen your understanding.
1) Mean = 3.18; s = 1.33; n = 22; df = 21; CI95 = [2.59, 3.77]
2) Mean = 3.46; σ = 1.25; n = 8; CI95 = [2.59, 4.33]
3) Mean = 4.1; s = 0.4; n = 240; df = 239 (but we will use the “200” row, since 239 is not in the t-table); = 1.972 * 0.4/SQRT(240) = 0.050916; ME = 0.050916 / 4.1 = 0.012419 = 1.24%
4) Mean = 12000; s = 3000; n = 18; df = 17; = 2.110 * 3000/SQRT(18) = 707.106781; ME = 707.106781 / 12000 = 0.058926 = 5.89%