Elementary Statistics: A Step-by-Step Approach with Formula Card 9th Edition

Published by McGraw-Hill Education
ISBN 10: 0078136334
ISBN 13: 978-0-07813-633-7

Chapter 6 - The Normal Distribution - 6-2 Applications of the Normal Distribution - Exercises 6-2 - Page 340: 39

Answer

The data set does not show normality. Please see below for explanations.

Work Step by Step

1. As shown in the figure, we first construct a frequency distribution and draw a histogram for the data. Clearly the histogram is strongly right skewed and it is not bell-shaped. 2. We use the Pearson coefficient (PC) to check for skewness. The mean is $\bar X=970.2$, median=$853.5$, standard deviation $s=376.5$. So $PC=\frac{3(970.2-853.5)}{376.5}=0.93$, this number is close to 1 indicating that the distribution is strongly skewed. 3. We check for outliers to see if any data lie outside $\pm1.5IQR$ of the mean. IQR can be found as 95 and 1.5IQR=132.5 giving a range of $\bar X-1.5IQR=837.7$ to $\bar X+1.5IQR=1102.7$ compare the data to this range, we found that 2084 1497 826 815 750 637 737 are outliers. Conclusion, the histogram does not show a bell-shaped distribution, the Pearson coefficient is close to 1 indicating a strongly right skewed distribution, and there are many outliers in the data set. The data set does not show normality.
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