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  • AMRI.-TR-66-220

    AUTOMATED READABILITY INDEX

    E. A. SMITH, EdO

    AEROSPACE MEDICAL RESEARCH LABORATORtIES

    'R. 1. SENTER, PhD

    UNIVERSITY OF CINCINNATI

    I APR 41968NOVEMBER 1967

    Dftr'hutfi6 64 this document is unimitd it

    may be released to the Clearinghouse, Depart-ment of, Commerce, for sale to the general public.

    ( LCLEARINGHOUSE

    : | , , : Sprin ,, ,, 22151

    AEROSPACE MEDICAL RESEARCH LABORATORIESE AEROSPACE MEDICAL DIVISION

    AIR FORCE SYSTEMS COMMANDWRIGHT-PATTERSON AIR FORCE BASE, OHIO

  • NOTICES-

    When-VS Government drawings, ,specifications, or other data are used for any -purpose other thana definitely -related Government procurement operation, the- Government thereby incurs 'no respon-Aibility noi~ any obligation Wvhatsoever, and the fact that the Government may-have formulated, fur-nished,, orin any way-,supplied, the said drawings, specifications, or other datit, is not to be regardedby Iiplication or otherwise, as-in any ~manner licenslrng'the ~holder or any other person or corpora-tion, or conveyingAny rights or-perniission top-anufacture, iise, Oz MIllany patented. inventionthat ma~y in- any vrsy be rplated- thereto.

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    -DDCCamneron StationAlexandria, Virgiia 22314

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    Do not retqrn this copy. -Retain -or destroy.

    ~uw ~~cii68 -CISS t-5t

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  • UNCLASSIFIED

    A~1 667 273AUTOMATED READABILITY INDEX

    R. J. Senter, et al

    University of CincinnatiCincinnati, Ohio

    November 1967

    Pros4for. ...

    DEFENSE DOCUMENTATION CENTERDEFENSE SUPPLY AGENCY

    FOR FEDERAL SCIENTIFIC AND TECHNICAL INFORMATION

    U. S. DEPARTMENT OF COMMERCE / NATIONAL BUREAU OF STANDARDS INSTITUTE FOR APPLIED TECHNOLOGY

  • AMRL-TR-66-220

    AUTOMATED READABILITY INDEX

    E. A. SMITH, EdD

    AEROSPACE MEDICAL RESEARCH LABORATORIES

    R. J. SENTER, PhD

    UNIVERSITY OF CINCINNATI

    .istriuLion of tlud' document is unlimited. Itmay be released/to the Clearinghouse, Depart-ment of Commerce, for sale to the general public.

  • Foreword

    This study represents a portion of the explcratory development program ofthe Technical Training Bianch of the Training Research Division. The zesearchwas conducted in part by the University of Cincinnati, under Contract AF 33(615)-1046. The work was in support of Project 1710, "Human Factors in the Design ofTraining Systems," Task 171007, "Automated Training and Programmed Instruc-tion." Dr. Gordon A. Eckstrand was the Project Scientist and Dr. Ross L. Morganwas the Task Scientist. The report covers research performed between August1964 and August 1966.

    The authors are indebted to Mr. Robert J. Roettele of the Research Instru-mentation Branch for the design and construction of the Tabulator.

    This technical report has been reviewed and is approved.

    WALTER F. GRETHER, PhDTechnical DirectorBehavioral Sciences LaboratoryAerospace Medical Research Laboratories

    111

  • Abstract

    Inasmuch as the utility of technical manuals is influenced to a marked extentby their reading difficulty or readability, the Automated Readability Index wasdevised to provide an easy, automated method of collecting data from whichtextual material can be evaluatczl in terms of readability. Whereas most read-ability formulae include separate jactors related to (1) word difficulty and (2)sentence difficulty, the Automate. Readability Index provides for the mechanicaltabulation of the required data on passages as they are typed on a standardtypewriter. Impulses from the typewriter activate counters which record thenumber of letters, words and sentences contained in the passage. From this, theaverage word length and average sentence length are computed. Appropriateweightings of -these factors result in an index reflecting the readability of the

    passage. This index is in close agreement with other indices of readability.

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  • SECTION I.

    IntroductionThe Air Force makes extensive use of written materials such as manuals, reports, staff studies,

    training documents, letters, etc. The readability of a document greatly influences the time requiredto extract needed information from the document. Likewise, it influences the probability that theinformation extracted will be correctly understood and used. The costly effects of inadequate con-munication are well-known. Deficiencies in written communications often could be precluded bythe preparation of more readable Air Force documents. An Automated Readability Index, as de-scribed in this report, offers a fast and economical means of obtaining an index of readability ofAir Force materials such as textbooks and technical manuals. Use of such an Automated Readabil-ity Index would contribute significantly to the efficiency of many Air Force operations.

    Since Chall (1958) provides an excellent source, no general review of the literature will beincluded here. Most readability indices, however, consist of two factors. One factor relates tosentence structure and is most generally a measure of the average number of words per sentence.The other factor generally relates to word structure and is usually based or, either the proportionof easy words determined with reference to word list (Dale and Chall, 1948) or the average num-r ber of syllables per word (Fleseh, 1951). While the word list has many advantages, especially in

    4the lower grades, it is both slow and relatively inaccurate when applied to adult reading material.As will be demonstrated, syllable counts prove to be deceptively unreliable.To explore the reliability of a syllable count, a passage selected at random from a textbook

    was presented to a class of 65 college students. This passage contained 169 syllables. The mem-bers of the class were instructed to count the number of syllables in the passage. The group'smean syllable count was 160.56. The standard deviation of the class' syllable count was 17.52,slightly more than 10 percent of tie mean. This indicates a considerable amount of variationamong syllable counters, and, consequently, of any readability based on such a count. Two weeksafter the initial administration of the syllable counting task, the same task was again presented tothe class. A "test-retest" reliability coefficient was .38 (N=64). It would appear that both inter-and intra-judge reliability for the task of syllable counting are untenable. The development ofthe Automated Readability Index is an attempt to avoid this unreliability without sacrificingvalidity.

    The Automated Readability Index is derived from ratios representing word difficulty (num-ber of letters per word) and sentence difficulty (number of words per sentence). The data fromwhich the index is calculated are collected through the use of an attachment to an electric type-writer. The attachment is refered to as a Readability Index Tabulator. The Tabulator is simplycomposed of three counters (Sodeco TCe F4E .25, TCe FSE .50, and TCe F6E .50) activatedby the keyboard of the electric typewriter (IBM Selectric, model 721). These counters tabulate(a) the number of strokes, (b) the number of words, and (c) the number of sentences containedin any passage being typed. Details of the Tabulator are shown in figures 1 thn 4.

    Any typist may operate this data tabulation system -. the primary modifications of standardtyping procedure necssitated by the system arc (1) an equal sign must be used in addition tothe period at the end of each sentence, and (2) the typist must space after the terminal word in

    each line. During the development of the formula, these modifications were observed to bet learned rather quickly and appeared to offer only minor and temporary interference with a typist's

    routine work.

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    FIgure 1. Typ.wrherwi0~ Tabulator

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    FIgure 2. PIckoff for Word Count

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    I Figure 3. PIckoff for Sentence Count3I _

  • View

    Figur* 4. Pickoff for Strokes Count (two views)

  • SECTION 11.Method

    Logically, the first consideration in -the developmentof the Automated Readability Index wasto establish that the -factors used relate to those found inoother indices. The factor relating tosentence structure (average number of words per sentence) is -identical to that found in mostcurrently used -indices so no verification oit was required. The verification of the relationshipbetween the word structure factor was also virtually selfLevident. However, since -the obvious-is at times not accurate, formal verification was accomplished with regards to the- relationshipbetween the ratio used here (letters per word) and that employed by Flesch (syllables per word).A sample of 20 one-syllable words was selected at-random from Webster's New International Die-tionary. Similar samples of t

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