What Readability Algorithm Scores Can Tell You
August 15, 2018
The origin of "readability tests" can be traced to America's earliest graded school systems. Rather than teaching young students in the full-blown vocabulary of a particular field of study, scholars developed primitive readability formulas to determine if their students would be able to digest scholastic content from books and papers. As the United States prepared to enter World War I, it was realized that many adult readers in our country had a very limited reading skills. This led to the U.S. Military to be proactive in determining how materials for adult education, such as textbooks, training guides and weapon manuals, should be written for maximum comprehension.
Origin and Development of Readability Formulas
There are currently more than 200 readability algorithms being applied with varying degrees of accuracy and success. These formulas do not measure comprehension and applied incorrectly can produce misleading results.
- Flesch Reading Ease Score - Rudolph Flesch's readability formula is one of the oldest and was developed using a simple approach to determine a recommended school grade-level of the reader based on a tabulated score of 0 to 100 with the higher score being the easiest to read content.
- Flesch-Kincaid Readability Test - Flesch-Kincaid Grade Level classifications are based on sentence length as judged by the average number of words in a sentence, as well as word length as judged by the average number of syllables in a word. The results are inversely correlated for reading ease and grade level.
- Gunning Fog Index - Developed in 1952, the index is commonly used to estimate the years of formal education required to understand content on a first reading. The Gunning Fog formula results in a grade-level readability score, so a writer's text is easily interpreted by the intended audience.
- Simple Measure of Gobbledygook - The SMOG grade is a measure of readability that estimates the years of education needed to understand consumer oriented healthcare messages and materials. The authors believed the Flesch-Kincaid underestimated reading difficulty when compared to the SMOG grade.
- Linsear Write Formula - The Air Force developed the readability formula to calculate readership needs for military technical manuals. Linsear Write determines the grade level based on sentence length and the number of words contained in the text with three or more syllables.
- Coleman—Liau Index - Since computer programs account for characters more readily and accurately than words, the Coleman—Liau Index does not rely on comparing syllables and complex word indices. Only the length of characters used to form the words analyzes content.
- Automated Readability Index - The ARI index was designed for real-time monitoring of content produced on electric typewriters. Unlike most readability formulas, it relies on characters per word (not syllables per word) and calculates the grade-level needed to comprehend English text.
Critics also blast the limitations of these indexing tools. However, if you apply the tools frequently and consistently, you will gain a better understanding as to which tool will work best for different types of content and audiences. Applied correctly, readability tools are excellent for writers, trainers, speakers, marketers and all website content providers. With the enormous amount of content being created and consumed online, it is important to ensure your message is readable by your target audience.