Basic Statistics: Tales of Distributions 10th Edition

Published by Cengage Learning
ISBN 10: 0-49580-891-1
ISBN 13: 978-0-49580-891-6

Chapter 4 - Exploring Data: Variability - Problems - Page 63: 4.9

Answer

See explanation

Work Step by Step

### **Step 1: Estimate the Larger Standard Deviation** #### Dataset a: 5, 4, 3, 2, 1, 0 * Range: $5 - 0 = 5$ * Fairly spread out, symmetrical #### Dataset b: 5, 5, 5, 0, 0, 0 * Range: $5 - 0 = 5$ * Split into two clusters (0s and 5s), with no middle ground **Estimate**: Distribution **b** is likely to have **larger** standard deviation due to the extreme clustering at both ends—values are farther from the mean than in a. --- ### **Step 2: Use the Raw-Score Formula** $$ S = \sqrt{\frac{\sum X^2 - \frac{(\sum X)^2}{N}}{N}} $$ --- ### **Compute for a: 5, 4, 3, 2, 1, 0** * $N = 6$ * $\sum X = 5 + 4 + 3 + 2 + 1 + 0 = 15$ * $\sum X^2 = 5^2 + 4^2 + 3^2 + 2^2 + 1^2 + 0^2 = 25 + 16 + 9 + 4 + 1 + 0 = 55$ $$ S_a = \sqrt{ \frac{55 - \frac{15^2}{6}}{6} } = \sqrt{ \frac{55 - 37.5}{6} } = \sqrt{ \frac{17.5}{6} } = \sqrt{2.9167} \approx 1.71 $$ --- ### **Compute for b: 5, 5, 5, 0, 0, 0** * $N = 6$ * $\sum X = 5 + 5 + 5 + 0 + 0 + 0 = 15$ * $\sum X^2 = 25 + 25 + 25 + 0 + 0 + 0 = 75$ $$ S_b = \sqrt{ \frac{75 - \frac{15^2}{6}}{6} } = \sqrt{ \frac{75 - 37.5}{6} } = \sqrt{ \frac{37.5}{6} } = \sqrt{6.25} = 2.5 $$ --- ### **Results** * $S_a \approx 1.71$ * $S_b = 2.5$ --- ### **Conclusion** * **Distribution b has the larger standard deviation**, confirming the visual estimate. * Both distributions have the **same range (5)**, but the values in b are clustered at the extremes, inflating the standard deviation. * **Raw-score formula and estimation align**.
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