Readability index provides an approximate number of years of education
that the reader would need to be able to understand the reading. The factors
that contibute to a high value of this score include words with lots of
syllables, sentences with a large number of words, large words, absence
of very short words, obscene words, and the use of numbers in the document.
A low value is 1, a high value is 15.
Readability index allows you to easily adjust the level of your readings
to ensure that you always practice on texts of adequate complexity. The
readability analysis feature is available in the RocketReader Gold and
RocketReader Educational editions.
the readability index for a reading, select View -> Analysis of Document
in the Practice Reading window (as shown below).
You can also check various other readability metrics of the text, as well
as grammar statistics.