Edward Fry of Rutgers University created the readability test to help teachers check the readability of text. The teacher randomly selects 100-word passages from a book or article. The teacher then counts the average number of sentences per 100 words and the average number of syllables. Numbers don't count toward the total; proper nouns do. Teachers can simply mark every syllable above the words and then count the marks. They then check their figures against a readability chart that covers readers ages 6 to 18.
The teacher can determine whether a book has uneven readability by testing different passages. When the samples vary greatly, the teacher should take more samples. After factoring in the average number of sentences and the length of the sentences, the teacher can look at the graph, which will indicate the text's appropriate age group.
Readability tests are not 100 percent accurate, and some books added to libraries because of their readability scores are too advanced for most students. Readability does not depend entirely on sentence and word length.
Readers can sometimes understand complex subjects when they're highly interested in the material and when the text has illustrations and other reading aids. Students who are highly familiar with a subject may read complex text more easily while struggling with works of similar complexity on unfamiliar subjects. Print legibility can also influence a student's ability to read the text. For example, people read boldfaced text more quickly than italics. Very long or short lines also make it harder for people to read quickly.