Are You a Fog Maker or a Clear Communicator?

Communication occurs only if the audience understands the message in the way you, as the writer intended–but how can you tell if your reader is likely to understand? 

Gobbledygook and bafflegab abound in technical writing. As scientists, it’s easy to think that the job of writing technically clear and easily understood prose isn’t as important as possessing the know-how to get the job done. Yet scientists spend a lot of time communicating (some studies suggest that at least 30 percent of each day), and often have to write to a variety of audiences including other scientists, co-workers (some who may not have technical backgrounds), researchers, policy makers, and others.

Consider report writing. Your primary audience is often the managerial decision-makers, but you also must include the secondary audience of production personnel, and maybe even a tertiary audience of marketing employees. Outside of your organization, you may also be engaged in writing persuasive messages to gain support and funding for your work. It’s easy to see how crucial the ability to write clearly and forcefully helps improve your productivity.

Because you’re often faced with how to tailor a message to a specific audience without compromising the quality of the technical information, it would be nice to be able to gauge just how readable your document is. It’s tough not to assume that your reader is as familiar as you are with your material.  So how do you measure how easy or difficult your message is to read? This is the purpose of scientific readability formulas.

And there are many! For example, there is the Dale-Chall, the New Dale-Chall, the Flesch-Kincaid, the SPACHE, and these are only a few. Some are available online for purchase and can be downloaded to your computer. Each is designed to analyze the words and sentences in your document and produce a readability score.
There’s also an easy one that you don’t have to purchase, can use easily, and provides you with a quick assessment of your document. It was designed by Robert Gunning, and is found in The Technique of Clear Writing.  It’s often referred to as the Fog index. Here’s how to calculate it:

The Gunning Fog Index (or FOG) Readability Formula

Step 1: Take a sample passage of at least 100-words and count the number of exact words and sentences.

Step 2: Divide the total number of words in the sample by the number of sentences to arrive at the Average Sentence Length (ASL).

Step 3: Count the number of words of three or more syllables that are NOT (i) proper nouns, (ii) combinations of easy words or hyphenated words, or (iii) two-syllable verbs made into three with -es and -ed endings.

Step 4: Divide this number by the number or words in the sample passage. For example, 25 long words divided by 100 words gives you 25 Percent Hard Words (PHW).

Step 5: Add the ASL from Step 2 and the PHW from Step 4.

Step 6: Multiply the result by 0.4.

The mathematical formula is:

Grade Level = 0.4 (ASL + PHW)


ASL = Average Sentence Length (i.e., number of words divided by the number of sentences)

PHW = Percentage of Hard Words

The FOG gives a snap-shot look at your document’s readability. For general readership, and those who are not technically inclined, the ideal score for readability is a FOG of 7 or 8. (The numbers correspond to grade level; here, it refers to the seventh or eighth grade.) Anything above 12 is considered difficult for many people to read. For instance, academic papers average around 15-20; magazines, like Time, Newsweek, and the Wall Street Journal average around 11; and many small town newspapers average around 6 to 8.
The FOG reportedly has an 80 percent correct outcome. Yet many limitations to readability formulas exist, and human judgment should override simplistic views provided by flawed quantitative results. Shorter and simpler sentences, for instance, reduce the Fog index but may not actually make the document more understandable. If you compute the index and find an outcome incompatible with your intended audience, go back and review your word choice and sentence construction. However, be careful not to write just to the index. In other words, contemplate the delicate balance, and look for ways to revise toward a style that is more agreeable to your reader.

Of course, because you’re scientist, after you revise it, you’ll want to measure it again!
By the way, can you guess what the FOG is for this article?

(ANSWER: 9.0)

1. Gunning, Robert. 1968. The Technique of Clear Writing, pp.38-39. New York: McGraw-Hill.

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