RESEARCH
SUMMARY
Over 80 years of research and testing have contributed to the worldwide use in many
languages of the readability formulas.
They help us improve the text on the level of words and sentences, the
first causes of reading difficulty.
The principles of readability are in every style manual. Readability formulas
are in every word processor. What is missing is the research and theory on which they stand.
The Principles of Readability
William H. DuBay
INTRODUCTION
In 1998, traffic accidents caused 46 percent of all accidental deaths of infants
and children aged 1 to 14 (National Center for Health Statistics, 2000). One
study (Johnston et al. 1994) showed that the single strongest risk factor for injury
in a traffic accident is the improper use of child-safety seats. Another study
(Kahane 1986) showed that, when correctly used, child safety seats reduce the
risk of fatal injury by 71 percent and hospitalization by 67 percent.
To be effective, however, the seats must be installed correctly. Other studies,
showed that 79 to 94 percent of car seats are used improperly (National Highway
Traffic Safety Administration 1996, Decina and Knoebel 1997, Lane et al.
2000).
Public-health specialists Dr. Mark Wegner and Deborah Girasek (2003)
suspected that poor comprehension of the installation instructions might
contribute to this problem. They looked into the readability of the instructions
and published their findings in the medical journal Pediatrics. The story was
covered widely in the media.
The authors referred to the National Adult Literacy Study (National Center for
Educational Statistics, 1993), which states the average adult in the U.S. reads at
the 7th grade level. They also cited experts in health literacy who recommend that
materials for the public be written at the fifth or sixth-grade reading level (Doak
et al., 1996; Weiss and Coyne, 1997).
Their study found that the average reading level of the 107 instructions they
examined was the 10th grade, too difficult for 80 percent adult readers in the U.S.
When texts exceed the reading ability of readers, they usually stop reading. The
authors did not address the design, completeness, or the organization of the
instructions. They did not say that the instructions were badly written. Armed
with the SMOG readability formula, they found the instructions were written at
the wrong grade level. You can be sure the manufacturers of the car safety seats
are scrambling to re-write their instructions.
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