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PG II(J) Determining An Instruction’s “Readability” Score.
The Federal Juridical Center suggests calculating a “readability” score for testing the ease of comprehension of instructions. This readability score is based on an index designed by Dr. Rudolph Flesch. (Flesch, Measuring the Level of Abstraction, 34 J. Applied Psychology 384 (1950).) This test combines into a single score two measures that are associated with ease of comprehension: (1) the average number of syllables per word and (2) the proportion of words that are concrete as contrasted with abstract. The test does not require much subjective judgment by the person doing the scoring and may, therefore, be said to be relatively objective. However, because any such test provides only an indirect and imperfect measure of comprehensive ability, the Federal Judicial Center added the following caveat:
“We would generally expect improvement in comprehensibility to be accompanied by improvement in Flesch scores, but it should not be assumed that instructions with higher Flesch scores are invariably more understandable than instructions with lower scores.” (Federal Judicial Center, p. 172.)
For purposes of the test, words are identified as uncommon based on Thorndike and Lorge (discussed in the preceding section). Thorndike and Lorge have determined that the if word is used less frequently than 10 times per million words of writing, then it is considered to be uncommon. (NOTE: The count of uncommon words is unduplicated: a word is counted only once even if it used more than once in a particular instruction.)
[See also FORECITE BIBLIO, “Language/Drafting of Instructions” (BIBLIO L)]