Misleading Graphs and Statistics

“Lies, damned lies, and statistics” Statistics are commonly used to make a point

or back-up one’s position 82.5% of all statistics are made up on the spot.

The “Average” Person… Be wary when politicians use the word

“average” when making a point. When the data are likely to be skewed, you

should ask: What kind of average did you use?

U.S. Income Distribution

Source: http://visualizingeconomics.com/2006/11/05/2005-us-income-distribution/11/8/2007 3:07 PM

Manipulating Information By adjusting the type and scale of graphical displays,

they can be used to highlight desirable information or (hide undesirable information). While this is not always bad, it should make you aware of

the danger of taking graphical displays at face value.

You should also be wary of the results of surveys, especially when you do not know how the survey was collected / administered / worded.

Sampling Issues Those being polled are not always honest!

(Imagine a cop surveying teens on drug use) E.g. “The Bradley Effect” -- an issue related to

race discrimination; getting a lot of airtime lately re: the election.

(There’s a “Reverse Bradley Effect” too!)

Is the sample biased (intentionally or not)? (Political polls of likely voters under-represent

cell-phone users)

Ways to Manipulate Graphs Scale and Axis Manipulation (Line, Bar

Graphs) Cropping to focus on desirable information

(Esp. w/ Line Graphs) Three dimensional effects (e.g., perspective &

“volume”) Pictorial Embellishments (e.g., “cartoon”

effects, leading the readers’ eye)

Starting Point Mayor Marcus is running for a second term against a

challenger. Which graph should he send to the local journalist who is reporting

on crime rates?

What’s wrong with this picture?

What’s wrong with this picture?

What’s wrong with this picture?

What’s wrong with this picture?

What’s wrong with this picture?

What’s wrong with this picture?

What’s wrong with this picture?

What’s wrong with this picture?

What’s wrong with this picture?

What’s wrong with this picture?

What’s wrong with this picture?

What’s wrong with this picture?

What’s wrong with this sample? A uniformed police officer surveys teens at a local

high school athletics competition about drug activity in the school.

Compare the following survey questions: “Should the university use trees harvested during

construction to build furniture in the new chemistry building?”

“Should the university cut down trees in the construction zone to use as furniture in the new chemistry building?”

What’s wrong with this sample? Third grade students are asked, “How nutritious are

your evening meals?”

Literary Digest magazine asked its subscribers to RSVP saying whether they would vote for Landon or for Roosevelt in the 1936 presidential election.