Week 1 – Part 2 of the Assigned Readings – Chapter 2 Week 1 – Part 2 of the Assigned Readings – Chapter 2 Week 1 – Part 2 of the Assigned Readings – Chapter 2 Week 1 – Part 2 of the Assigned Readings – Chapter 2
The Five-Number Summary and Boxplots
To get a quick summary of both center and spread, combine all five numbers.
The five-number summary if a distribution consists of the smallest observation,
the first quartile, the median, the third quartile, and the largest observation, written
in order from the smallest to largest. In symbols, the five-number summary is
“Minimum Q1 M Q3 Maximum.”
The five-number summary of a distribution leads to a new graph, the boxplot.
A boxplot is a graph of the five-number summary.
- a central box spans the quartiles Q1 and Q3.
- A line in the box marks the median M.
- Lines extend from the box out to the smallest and largest observations.
When you look at a boxplot, first locate the median, which marks the center of the
distribution. Then look at the spread. The span of the central box shows the
spread of the middle half of the data, and the extremes (smallest and largest
observations) show the spread of the entire data set. Week 1 – Part 2 of the Assigned Readings – Chapter 2
Figure 2.1 (the boxplot)
Travel times to work are in general a bit longer in New York than in North Carolina.
The median, both quartiles, and the maximum are all larger in New York. New York
travel times are also more variables. New York data are more strongly