Statistics (12th Edition)

Published by Pearson
ISBN 10: 0321755936
ISBN 13: 978-0-32175-593-3

Chapter 2 - Methods for Describing Sets of Data - Exercises 2.71 - 2.89 - Learning the Mechanics - Page 64: 2.78b

Answer

Range =$6$ Sample variance = $s^{2}=3.619$ Sample standard deviation = $s = 1.9$

Work Step by Step

Recall the shortcut formula for calculating the variance ($s^{2}$)$:$ $$s^{2}=\frac{\sum x_{i}^{2}-\frac{(\sum x_{i})^{2}}{n}}{n-1}$$ Let's create a table in which we compute $\displaystyle \sum x_{i}$ and $\displaystyle \sum x_{i}^{2}$: $$ \begin{array}{lll} & x & x^{2}\\ \hline & 1 & 1\\ & 6 & 36\\ & 2 & 4\\ & 2 & 4\\ & 3 & 9\\ & 0 & 0\\ & 3 & 9\\ \hline\rm Sum & 17 & 63 \end{array}$$ Plug in the given values (there are $n=7$ data items): $$\begin{align*} s^{2}&= \displaystyle \frac{63-\frac{(17)^{2}}{7}}{7-1} & & \\ & = 3.619 \\\\ s&= \sqrt{3.619} =1.90 \end{align*}$$ The range is the difference between the largest and smallest data item: $6-0=6$
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