Total neglect
Sep 19, 2005
The Northern Trust advertisement is a great instructional tool, and Michael Anderson captured its key aspects in these comments. Michael, by the way, has an interesting blog too on teaching statistics.
Gridlines, choice of scale, dependent and independent variables, data-ink ratio, linear interpolation, sample size are all issues raised by the chart. While we can't expect advertisers to be rigorous about charts, it is appalling to see the total neglect of all of these issues.
You know, that truly is a terrible graphic but there is one oddball twisted way in which it could be construed to make sense -- or rather, a poor representation of something that could have made sense: if the graphic was supposed to be some sort of state-space plot. In that case, the axes don't represent dependent and independent variables. The dot that we see then shows the state of the quarter and the state of one's personal life.
Here's an example that shows the path of defense and non-defense discretionary spending over time:
http://anonymous.coward.free.fr/scpo/spending-components-real.png
Here's another example that shows revenues and outlays:
http://anonymous.coward.free.fr/scpo/deficit.png
Posted by: Robert | Sep 20, 2005 at 04:09 AM