The Text Stats feature calculates a variety of statistics for each
book in the Search Inside!™ program. The Readability calculations
estimate how easy it is to read and understand the text of a book.
- The Fog Index was developed by Robert Gunning. It indicates the
number of years of formal education required to read and understand a
passage of text.
- The Flesch Index, developed in 1940 by Dr. Rudolph Flesch, is
another indicator of reading ease. The score returned is based on a
100 point scale, with 100 being easiest to read. Scores between 90 and
100 are appropriate for 5th and 6th graders, while a college degree is
considered necessary to understand text with a score between 0 and
- The Flesch-Kincaid Index is a refinement to the Flesch Index that
tries to relate the score to a U.S. grade level. For example, text
with a Flesch-Kincaid score of 10.1 would be considered suitable for
someone with a 10th grade or higher reading level.
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