Editing Readability (section)

== Readability formula accuracy ==

The correlation with comprehension as measured by reading tests is as follows:<ref name="Gray" /><ref name="DuBay" />

{| class="wikitable"
!Formula
!Correlation
!Standard Error
|-
| Gray & Leary (1935) || .645 ||
|-
| Flesch‐Kincaid (1948) || .91 || 1.9
|-
| Flesch Reading Ease (1948) || .88 || 2.44
|-
| Original Dale‐Chall (1948) || .93 || 1.76
|-
| Gunning Fog (1952) || .91 || 2.00
|-
| Fry Graph (1963) || .86 || 2.31
|-
| McLaughlin Smog (1969) || .88 || 2.28
|-
| FORCAST (1973) || .66 || 3.61
|}

The accuracy of readability formulas increases when finding the average readability of a large number of works. The tests generate a score based on characteristics such as [[statistical average]] word length (which is used as an unreliable proxy for [[semantic]] difficulty; sometimes [[word frequency]] is taken into account) and sentence length (as an unreliable proxy for [[syntactic]] complexity) of the work.

Most experts agree that simple readability formulas like [[Flesch–Kincaid readability tests|Flesch–Kincaid grade-level]] can be highly misleading.<ref name="KlareBuck3" /> Even though the traditional features like the average sentence length have high correlation with reading difficulty, the measure of readability is much more complex. The [[artificial intelligence]], data-driven approach (see above) was studied to tackle this shortcoming.<ref name="Gunning2" />

Writing experts have warned that an attempt to simplify the text only by changing the length of the words and sentences may result in text that is more difficult to read.<ref name="Fleschwrite2">{{cite book |last=Flesch |first=R. |title=The Art of Readable Writing |publisher=Harper |year=1949 |location=New York |oclc=318542 |author-link=Rudolf Flesch}}</ref> All the variables are tightly related. If one is changed, the others must also be adjusted, including approach, voice, person, tone, typography, design, and organization.

Writing for a class of readers other than one's own is very difficult. It takes training, method, and practice.<ref name="FleschArt2">Flesch, R. 1946. ''The art of plain talk.'' New York: Harper.</ref> Among those who are good at this are writers of novels and children's books. The writing experts all advise that, besides using a formula, observe all the norms of good writing, which are essential for writing readable texts. Writers should study the texts used by their audience and their reading habits.<ref name="FleschPlain2">Flesch, R. 1979. ''How to write in plain English: A book for lawyers and consumers''. New York: Harpers.</ref> This means that for a 5th-grade audience, the writer should study and learn good quality 5th-grade materials.<ref name="KlareEnglish2">Klare, G. R. 1980. ''How to write readable English.'' London: Hutchinson.</ref><ref name="Frywriting2">Fry, E. B. 1988. "Writeability: the principles of writing for increased comprehension." In ''Readability: Its past, present, and future'', eds. B. I. Zakaluk and S. J. Samuels. Newark, DE: International Reading Assn.</ref>