Flesch–Kincaid readability tests

"The Flesch–Kincaid" (F–K) reading grade level was developed under contract to the U.S. Navy in 1975 by J. Peter Kincaid and his team.

[1] Related U.S. Navy research directed by Kincaid delved into high-tech education (for example, the electronic authoring and delivery of technical information),[2] usefulness of the Flesch–Kincaid readability formula,[3] computer aids for editing tests,[4] illustrated formats to teach procedures,[5] and the Computer Readability Editing System (CRES).

[6] The F–K formula was first used by the Army for assessing the difficulty of technical manuals in 1978 and soon after became a United States Military Standard.

Pennsylvania was the first U.S. state to require that automobile insurance policies be written at no higher than a ninth-grade level (14–15 years of age) of reading difficulty, as measured by the F–K formula.

The highest (easiest) readability score possible is 121.22, but only if every sentence consists of only one-syllable words.

The sentence "The Australian platypus is seemingly a hybrid of a mammal and reptilian creature."

While Amazon calculates the text of Moby-Dick as 57.9,[8] one particularly long sentence about sharks in chapter 64 has a readability score of −146.77.

[9] One sentence in the beginning of Scott Moncrieff's English translation of Swann's Way, by Marcel Proust, has a score of −515.1.

[11] Florida requires that insurance policies have a Flesch reading ease score of 45 or greater.

[12][13] Use of this scale is so ubiquitous that it is bundled with popular word processing programs and services such as KWord, IBM Lotus Symphony, Microsoft Office Word, WordPerfect, WordPro, and Grammarly.

The sentence, "The Australian platypus is seemingly a hybrid of a mammal and reptilian creature" is an 11.3 as it has 24 syllables and 13 words.

As readability formulas were developed for school books, they demonstrate weaknesses compared to directly testing usability with typical readers.

They neglect between-reader differences and effects of content, layout and retrieval aids.