Descriptive Statistics II:
ADDITIONAL DESCRIPTIVE MEASURES AND DATA DISPLAYS
After completing the chapter, you should be able to
- Determine percentile and quartile values and measure dispersion using the interquartile range.
- Construct and interpret box plots and stem-and-leaf diagrams.
- Identify outliers in data sets.
- Compute and interpret two important measures of association: covariance and correlation coefficient.
- Calculate the coefficient of variation, the geometric mean and the weighted average and explain their role as descriptive measures.
Percentiles Make Headlines
For statisticians, regardless of political leaning, one of the more remarkable aspects of the “Occupy Wall Street” movement that began in October 2011 was seeing percentiles move out of the textbooks and into the streets, the headlines, and even onto bumper stickers. In declaring “we are the 99%,” the “Occupy” protesters brought renewed focus to the issue of economic inequality by separating Americans into two groups: those whose economic position fell below the 99th percentile—the “ninety-nine percent”—and those whose economic position put them above that 99th percentile—the “top 1 percent.”
To fully understand the point being made by those calling themselves ...