qnt homework

We have explained how to create good graphs. Now, let’s turn things around. As an impartial consumer of information,

you need a checklist of errors to beware. Those who want to slant the facts may do these things deliberately, although

most errors occur through ignorance. Use this list to protect yourself against ignorant or unscrupulous practitioners of

the graphical arts.

Error 1: Nonzero Origin NonZero

A nonzero origin will exaggerate the trend. Measured distances do not match the stated values or axis demarcations.

The accounting profession is particularly aggressive in enforcing this rule. Although zero origins are preferred,

sometimes a nonzero origin is needed to show sufficient detail.

Error 2: Elastic Graph Proportions Elastic

By shortening the X-axis in relation to the Y-axis, vertical change is exaggerated. For a time series (X-axis

representing time) this can make a sluggish sales or profit curve appear steep. Conversely, a wide X-axis and short Y-

axis can downplay alarming changes (recalls, industrial accidents). Keep the aspect ratio (width/height) below 2.00.

Excel graphs use a default aspect ratio of about 1.8. The Golden Ratio you learned in art history suggests that 1.62 is

ideal. Older TV screens use a 1:33 ratio as do older PCs (640 ! 480 pixels). Movies use a wide-screen format (up to

2.55) but VHS tapes and DVDs may crop it to fit on a television screen. HDTV and multimedia computers use a 16:9

aspect ratio (about 1.78). Charts whose height exceeds their width don’t fit well on pages or computer screens.

Source: Statistical Abstract of the United States, 2002, p. 707.

Error 3: Dramatic Title

The title often is designed more to grab the reader’s attention than to convey the chart’s content (Criminals on a

Spree, Deficit Swamps Economy). Sometimes the title attempts to draw your conclusion for you (Inflation Wipes Out

Savings, Imports Dwarf Exports). A title should be short but adequate for the purpose.

Error 4: Distracting Pictures

To add visual pizzazz, artists may superimpose the chart on a photograph (e.g., a gasoline price chart atop a photo of

Middle East warfare) or add colorful cartoon figures, banners, or drawings. This is mostly harmless, but can distract the

reader or impart an emotional slant (e.g., softening bad news about the home team’s slide toward the cellar by drawing

a sad-face team mascot cartoon).

Error 5: Authority Figures

Advertisements sometimes feature mature, attractive, conservatively attired actors portraying scientists, doctors, or

business leaders examining scientific-looking charts. Because the public respects science’s reputation, such displays

impart credibility to self-serving commercial claims.

Error 6: 3-D and Rotated Graphs MedSchool

By making a graph 3-dimensional and/or rotating it through space, the author can make trends appear to dwindle into

the distance or loom alarmingly toward you. This example combines errors 1, 3, 4, 5, and 6 (nonzero origin, leading

title, distracting picture, vague source, rotated 3-D look).

3.11 Deceptive Graphs (See related pages)

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Chapter 3

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Source: American Medical Association.

Error 7: Missing Axis Demarcations

Without "tick" marks on the axis, the reader cannot identify individual data values. Grid lines help the viewer compare

magnitudes but are often omitted for clarity. For maximum clarity in a bar graph, label each bar with its numerical

value, unless the scale is clearly demarcated and labeled.

Error 8: Missing Measurement Units or Definitions

Missing or unclear units of measurement (dollars? percent?) can render a chart useless. Even if the vertical scale is in

dollars, we must know whether the variable being plotted is sales, profits, assets, or whatever. If percent, indicate

clearly percentage of what.

Error 9: Vague Source

Large federal agencies or corporations employ thousands of people and issue hundreds of reports per year. Vague

sources like "Department of Commerce" may indicate that the author lost the citation, didn’t know the data source, or

mixed data from several sources. Scientific publications insist on complete source citations. Rules are less rigorous for

publications aimed at a general audience.

Error 10: Complex Graphs

Complicated visual displays make the reader work harder. Keep your main objective in mind. Omit "bonus" detail or

put it in the appendix. Apply the 10-second rule to graphs. If the message really is complex, can it be broken into

smaller parts? This example on the next page combines errors 3, 4, 7, 8, 9, and 10 (silly subtitle, distracting pictures,

no data labels, no definitions, vague source, too much information).

Source: Hospital reports.

Error 11: Gratuitous Effects

Slide shows often use color and special effects (sound, interesting slide transitions, spinning text, etc.) to attract

attention. But once the novelty wears off, audiences may find special effects annoying.

Error 12: Estimated Data

In a spirit of zeal to include the "latest" figures, the last few data points in a time series are often estimated. Or

perhaps a couple of years were missing or incompatible, so the author had to "fill in the blanks." At a minimum,

estimated points should be noted.

Error 13: Area Trick AreaTrick

One of the most pernicious visual tricks is simultaneously enlarging the width of the bars as their height increases, so

the bar area misstates the true proportion (e.g., by replacing graph bars with figures like human beings, coins, or gas

pumps). As figure height increases, so does width, distorting the area.

Final Advice

Can you trust any visual display (unless you created it yourself)? Be a skeptic, and be pleasantly surprised if the graph

lives up to the best standards. Print media compete with TV and the Web, so newspapers and magazines must use

colorful charts to attract reader interest. People enjoy visual displays, so we accept some artistic liberties. Mass-

readership publications like U.S. News & World Report, Maclean’s, Time, Newsweek, USA Today, or even the more

specialized business-oriented publications like Forbes, Fortune, BusinessWeek, and The Wall Street Journal should not

be judged by the same standards you would apply to an academic journal. Businesses want charts that follow the rules,

because a deceptive chart may have serious consequences. Decisions may be made about products or services that

affect lives, market share, and jobs (including yours). So know the rules, try to follow them, and expect your peers and

subordinates to do the same. Catchy graphics have a place in selling your ideas but shouldn’t dominate the data.

Further Challenges

If you enjoy playing with computers, try to learn these skills on your own:

• Copy and paste Excel charts into Word or PowerPoint.

• Copy and paste charts from other software (MINITAB, Visual Statistics).

• Use screen captures and edit the results in Paint if necessary.

• Use presentation software (e.g., PowerPoint) with transition effects.

• Know how (and when) to link Excel charts to spreadsheets.

• Use clip art and create your own simple graphics.

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