MathCS.org - Statistics
3.5. Bending the Rules
Using graphical data representation provides a great opportunity to visualize data so that it conveys a particular point of view. This is not cheating, it is simply using some visual aides to make your data appear to support one particular point of view over another.
Here is, for example, a table of how much different states spend per students in dollars in 1980:
State
$ per Student
State
$ per Student
Arkansas
$1219
Idaho
$1345
Mississippi
$1189
New Jersey
$2576
North Dakota
$1607
Washington
$2079
Suppose we want to give a presentation in which the state of Arkansas looks reasonably good as compared to the state of New Jersey. We would create a bar char that minimizes the differences in state spending by using a particularly "large" scale on the y-axis:
We are kind of de-emphasizing the empty space that results in choosing a large y-scale by placing the chart title into that area.
Now we want to give a presentation in which the state of Arkansas looks very bad as compared to the state of New Jersey. We simply pick a scale on the y-axis that makes sure that the difference between Arkansas and New Jersey appears as larges as possible. In particular, we choose a y-scale that starts at 1000 and ends at 2400, instead of more standard values such as 0 to, say, 3000.
We also picked an "aggressive" color (red) for the Arkansas figure and a "calm" color (green) for New Jersey, emphasizing the fact that we want to represent Arkansas as "bad" and New Jersey as "good".
Both charts represent the same data, and both charts are perfectly valid. Yet visually they tell different stories. There are many other tricks that are used frequently to represent data in such as way as to support one particular point of view without outright misrepresenting reality.