Guidelines for readability

In works about technical communication, we are often told how to avoid such problems. For example, JoAnn Hackos and Dawn Stephens in Standards for Online Communication (1997) ask us to "conform to accepted style standards." They explain:

Many experts, through much research, have compiled golden rules of documentation writing. These rules apply regardless of medium:

• Use short, simple, familiar words
• Avoid jargon.
• Use culture-and-gender-neutral language.
• Use correct grammar, punctuation, and spelling.
• Use simple sentences, active voice, and present tense.
• Begin instructions in the imperative mode by starting sentences with an action verb.
• Use simple graphic elements such as bulleted lists and numbered steps to make information visually accessible.

For more suggestions, we recommend referring to one of many excellent books on writing style, especially technical style.

We all know of technical publications that do not follow these guidelines and are read only by a small fraction of the potential readership. One reason may be that the writers are not familiar with the background and research of these guidelines.

This paper looks most carefully at two of the most important elements of communication, the reading skills of the audience and the readability of the text.

The readability formulas

In the 1920s, educators discovered a way to use vocabulary difficulty and sentence length to predict the difficulty level of a text. They embedded this method in readability formulas, which have proven their worth in over 80 years of application.

Progress and research on the formulas was something of a secret until the 1950s. Writers like Rudolf Flesch, George Klare, Edgar Dale, and Jeanne Chall brought the formulas and the research supporting them to the marketplace. The formulas were widely used in journalism, research, health care, law, insurance, and industry. The U.S. military developed its own set of formulas for technical-training materials.

By the 1980s, there were 200 formulas and over a thousand studies published on the readability formulas attesting to their strong theoretical and statistical validity.

Are the readability formulas a problem?

In spite of the success of the readability formulas, they were always the center of controversy. When the "plain language" movement in the 1960s resulted in legislation requiring plain language in public and commercial documents a number of articles attacked the use of readability formulas. They had titles like, "Readability: A Postscript" (Manzo 1970), "Readability: Have we gone too far?" (Maxwell 1978), "Readability is a Four-letter Word" (Selzer 1981), "Why Readability Formulas Fail" (Bruce et al. 1981), "Readability Formulas: Second Looks, Second Thoughts" (Lange 1982), "Readability Formulas: What's the Use?" (Duffy 1985) and "Last Rites for Readability Formulas in Technical Communication" (Connaster 1999).