Readability scores
There are many factors which affect any reader's comprehension of what you
write. Various means of measuring readability have been developed.
Fog Index
UK newspapers employ the Fog index when sub-editing pieces for inclusion. To estimate:
- Select a passage with 100 words with complete sentences, even if you go
slightly above or below exactly 100 words .
- Find the average sentence length
(ASL) by dividing the number of sentences in the passage by the number of
words.
- Count the affixes - A.
- Count the names and personal pronouns -
P.
-
Subtract the number of personal references from the number of affixes.
Then feed the numbers into the equation:
ASL+(A-P)/ASL
The scale:
 | <20 Easy |
| >36 is fairly difficult and |
| Above 50 is unreadable! |
Gunning Fog Index
A modification of the Fog index counts the number of ‘hard words’. Select a
sample and work out the average sentence length. Now count the words with three
or more syllables but exclude
| Jargon |
| Easy words like ‘typewriter’, ‘newsletter’ |
| Verb forms ending in 'es', 'ing', or 'ed' |
| Proper nouns |
(ASL + HW) X 0.4
The average person reads at level 9. Easy reading range is 6-10 and
anything above 15 is getting difficult.
You can avoid the maths involved in working out the index. If you let MS Word check a document’s spelling and grammar, it can
work our some readability scores.
Word compiles the average number of syllables per word (ASW) and words per
sentence (ASL) which it uses to calculate readability ratings.
Flesch Reading Ease score
| The formula for the Flesch Reading Ease score is: |
206.835 – (1.015 x ASL)
– (84.6 x ASW)
| This rates text on a 100-point scale; the higher the score, the easier it
is to understand the document with 60 to 70 being an acceptable score for
literate adults.
|
Flesch-Kincaid Grade Level score
| The formula for the Flesch-Kincaid Grade Level score is: |
(.39 x ASL) +
(11.8 x ASW) – 15.59
| It is designed for US school level. So a score of 8.0 (13ish) means that an
eighth grader can understand the document.
|
Reference:
The Technique of Clear Writing - Gunning (out of print but most
college libraries should stock it).
© writersservices.com 2004
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