PEDIATRICS Vol. 111 No. 3 March 2003, pp. 588-591
How Readable Are Child Safety Seat Installation Instructions?
From the Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, Bethesda, Maryland
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
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Objectives. To measure the required reading level of a sample of child safety seat (CSS) installation instructions and to compare readability levels among different prices of CSSs to determine whether the lower cost seats to which low-income parents have greater access are written to a lower level of education.
Methods. A CD-ROM containing CSS installation instructions was obtained from the National Highway Traffic Safety Administration. Pricing information was obtained for available models from an Internet-based company that provides comparative shopping information. Paper copies of the instruction sets were generated, and their readability levels were determined using the SMOG test. A second rater was used in addition to the primary investigator to assess interrater reliability of the SMOG as applied to the instruction sets.
Results. The readability of instruction sets ranged from the 7th- to 12th-grade levels, with an overall mean SMOG score of 10.34. No significant associations were found to exist between readability and seat prices; this was observed whether the data were treated as continuous or categorical.
Conclusions. CSS instruction manuals are written at a reading level that exceeds the reading skills of most American consumers. These instruction sets should be rewritten at a lower reading level to encourage the proper installation of CSSs.
Key Words: car seats • safety • installation • instructions • readability • children • injury prevention
Abbreviations: MVC, motor vehicle collision • CSS, child safety seat • NHTSA, National Highway Traffic Safety Administration
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
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Motor vehicle collisions (MVCs) are a leading cause of death in infants and children. In fact, in 1998, injuries resulting from MVCs accounted for 46% of all unintentional injury-related deaths among children aged 1 to 14.1 Scientific evidence indicates that the single strongest risk factor for injury in an MVC is the nonuse of a restraint,2 with correctly used child safety seats (CSSs) reducing the risk of fatal injury by 71% and hospitalization by 67%.3 For child restraints to be optimally effective, however, they must be installed correctly, yet we know from numerous studies that improper restraint use is alarmingly prevalent, ranging from 79% to 94%.4–6
The underlying reasons for such a high rate of misuse of this important child safety device are not well understood. Possible contributors include engineering/design problems, physical difficulty with installation, and poor comprehension of installation instructions. Improvements in engineering and design have been made over the years in an attempt to improve ease of use. Legislation has also been enacted to improve uniformity and ease of installation, including the mandated development of upper tether straps and lower anchoring systems. As of September 2002, all new cars are required to feature these safety enhancements.7 These advances will not yield immediate benefits, however. Many older cars and CSSs will remain in circulation, particularly among lower-income families. Therefore, the comprehensibility of current installation instructions is likely to influence parent compliance with this important safety recommendation into the foreseeable future.
Poor comprehension often occurs when the required reading level of a particular text exceeds the reading capacity of the target population. In this situation, patients often become fatigued and discouraged, which may affect compliance.8 This issue is important to consider when developing health-related instructions because illiteracy is a problem of great importance in the United States. A 1992 survey by the US Department of Education’s National Center for Education Statistics estimated that 21% of the adult population—>40 million Americans older than 16 years—had only rudimentary reading and writing skills (ie, they read at or below the fifth-grade level). Another 25% (50 million) were classified as being "marginally literate" (ie, they read at or below approximately the eighth-grade level). The survey also reported that people of lower socioeconomic status tend to have lower literacy levels.9 It is interesting to note that incorrect utilization of CSSs has also been correlated with a lower level of socioeconomic status.10
The impact of literacy on health has also been well documented in the literature,11 and the readability of health-related materials has been the subject of increasing scientific scrutiny.12–16 We identified only 1 article that dealt with child safety and literacy, however, and it did not address CSS installation.17
In this study, we measured the required reading level of CSS installation instructions to determine whether readability poses a potential barrier to correct installation. An additional objective of the study was to compare readability levels among different price categories of CSSs. The main reason for this second analysis was to determine whether the lower cost seats that are more accessible to low-income parents financially are also more accessible to them from the perspective of literacy.
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METHODS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
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Sample
The instruction sets used for the purposes of this study came from a CD-ROM distributed by the National Highway Traffic Safety Administration (NHTSA). "Manufacturers’ Instructions for Child Safety Seats 1999 Edition" became available in March 2001 and contains instruction sets for different manufacturers and models current through 1999.18 NHTSA’s CD-ROM was chosen in recognition of its comprehensiveness and uniformity. It included instruction sets for every major CSS manufacturer, as verified by cross-referencing lists obtained from the American Academy of Pediatrics, NHTSA, and SafetyBeltSafe U.S.A.19–21 The CD-ROM features 140 different instruction sets, covering 11 manufacturers. Finally, the instruction sets represent materials on the market in 1 time frame (current through 1999).
Paper copies of all of the 140 instruction sets were generated with a laser printer. Certain exclusion criteria were then applied to generate our final study sample. Any instruction sets that dealt only with tether straps or harnesses were excluded because they were not specific to any particular model. Instruction sets unique to Canada were excluded. When there were multiple versions of US instruction sets for the same particular model on the ROM, only the most recent version was included. When apparent duplicates were undated, 1 of the sets was chosen at random to be tested. After these criteria were applied, each manufacturer on the CD-ROM was represented with at least 1 model, leaving a final sample for analysis of 107.
Pricing information for some of the CSS models was then obtained from epinions.com,22 an Internet-based company that provides comparative shopping information for consumers. This source was chosen both for uniformity and for quantity of price information. Attempts to obtain pricing information from manufacturers’ web sites were not successful because only a few contained pricing information. Of the numerous sources reviewed, epinions.com had pricing information for the most models in the study (n = 35).
Measurement
The SMOG test was chosen for performing readability tests on the samples. The SMOG test was introduced by McLaughlin in 196923 and has been used extensively to analyze health-oriented literature. In addition, it is adaptable to small sample sizes. Instructions for how to perform the SMOG test were obtained from a National Institutes of Health publication.24 The basic provisions of the test include selecting 3 10-sentence samples (1 each from near the beginning, middle, and end of the desired text) and then counting the number of polysyllabic words (containing 3 or more syllables) in that sample. This information is then used to calculate the reading ability (measured as school grade reading level) required for a person to comprehend that particular text.
For standardizing our sample of instruction text, 10 sentences in each of the following 3 distinct section types were tested for all sets: 1) the general warning section that preceded specific instructions, 2) a section describing how to install the seat, and 3) a section dealing with finer points of installation, such as proper selection of seat belts or adjustment of harness straps. These sections were chosen as they related most closely to the issue of injury prevention. Headings were not tested unless they were part of a sentence. Pictures and diagrams were not considered, neither were captions that stood apart from the rest of the instruction set and applied only to pictures. Federal law25 mandates that certain language must be included in all instruction sets. These passages were tested separately from the instruction sets and were not included in our statistical analyses.
Although the SMOG test is a fairly objective test, it still allows room for subjectivity in measurement. Words such as "different" and "reference," for example, are listed in the dictionary with 2- and 3-syllable pronunciations, necessitating a judgment call on the part of a readability rater. To ensure that the test methods lent themselves to reliable administration, a second reviewer was used to apply the SMOG to approximately 25% of the instruction sets tested. This subset was selected by including the first instruction set from every manufacturer, and then including every fifth instruction set from within each manufacturer. The second reviewer was given the same instruction set for the SMOG that was used by the principal investigator and tested the same passages.
Statistical Analysis
SMOG scores as well as available pricing information for each CSS model were analyzed using SPSS (Release 10.0.5).26 Basic descriptive statistics were generated, including mean readability level overall and mean readability by manufacturer, with 95% confidence intervals for samples larger than 10.
When examination of available data did not suggest any obvious price cutoff points, the samples were divided into the lower, middle, and upper thirds using a Microsoft Excel27 spreadsheet. This trifurcation resulted in categories labeled low ($80 or less), medium ($81–$116), and high (>$116). A Kruskal-Wallis test was then used to determine whether the readability of the instructions varied by CSS price category. Prices were also treated as continuous data and analyzed using a nonparametric correlation.
For exploring whether brand or model names that consisted of 3 or more syllables (eg, "Century," "Champion Scout Trooper") had biased the grade level of these samples, a Mann-Whitney test was performed. For determining reliability of the SMOG, a 
statistic was calculated to compare the scores of the 2 raters.
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RESULTS |
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The readability scores of the installation instructions we tested ranged from 7th to 12th grade, with a median and mode of 10 (see Table 1 for a frequency distribution of scores). The overall mean SMOG readability score was 10.34 (95% confidence interval: 10.16–10.52). The SMOG range varied by manufacturer: 7 to 12 (Britax, Charlotte, NC), 8 to 12 (Kolcraft, Chicago, IL), 9 to 11 (Evenflo, Piqua, OH), 9 to 12 (Cosco, Columbus, IN; Century, Macedonia, OH), 10 to 11 (Graco, Exton, PA), 10 to 12 (Fisher-Price, East Aurora, NY), and 11 to 12 (Guardian). When evaluated separately, the wording sections required by federal regulation also tested at the 10th-grade level.
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For the instruction sets for which pricing information was available (n = 35), the mean price was $109 with a range of $58 to $270. A Kruskal-Wallis test did not show any significant difference in readability among the 3 price categories that we created (P = .80). Readers who are interested in reviewing a complete listing of readability scores and pricing information for each model tested may contact the authors for more information. The raw price data were also plotted against SMOG score (Fig 1). When the price information was analyzed in its original continuous form, a Spearman rank correlation of price versus readability yielded similar (ie, nonsignificant) results (r = -0.04, P = .82).
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When analyzed separately models for which either the manufacturer or the model name or both had >3 syllables (n = 65) and had a mean readability score of 10.34 and a median of 10.0. Those with shorter names (n = 42) had a mean score of 10.33 and a median of 10.5. When a Mann-Whitney test was applied, this small difference between the 2 groups was not statistically significant.
Of the 29 samples tested by both the primary researcher and a second reviewer, agreement was achieved on 25 of 29 samples, resulting in a statistic of 0.80 (P < .001).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
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Our data indicate that CSS instructions in the United States are currently written at a reading level that is too high. Experts in the arena of health literacy recommend that materials be targeted to the fifth- or sixth-grade reading level.8, 11 The average readability level of the instruction sets that we tested was 10th grade. Researchers in a Louisiana study found that approximately two thirds of parents tested in an outpatient clinic could not read at more than a ninth-grade level.14 Because parents would be expected to be the main target audience for CSS instruction sets, this lends additional evidence that the instruction sets may not be reaching the people most likely to benefit from the message.
Overall, there did not seem to be any significant difference in readability among different price categories. This suggests that manufacturers are not targeting instructions to different market segments, at least with regard to reading level.
This study did not take into account some factors that tend to increase comprehensibility, such as the use of illustrations and empty space.8 The main reason this was not done was because images that were generated from the CD-ROM lost resolution.
In addition, parents may not even read the instruction manuals that come with their CSS or may receive second-hand seats that come without instructions, so the importance of instructions in the proper installation of CSS is unclear. In focus groups sponsored by the NHTSA, however, parents reported referring to written instructions when they ran into difficulties.28
Education efforts combined with recent engineering advances can be important complements of CSS instruction sets. With regard to newborns, the American Academy of Pediatrics currently recommends that all infant discharge policies include parent education on CSS installation, regular review of educational materials, and periodic in-service education for responsible staff.29 Pediatric clinics and practices represent another excellent opportunity for delivering personal messages to the target audience, and hands-on instruction has been shown to decrease the numbers of errors in CSS installation.5 Information on available training opportunities throughout the United States is available from NHTSA through its web site at www.nhtsa.dot.gov/people/injury/childps/Training/index.html or via a hotline at 1–800-424–9393.
Engineering improvements may indeed prove to be the most important factor in decreasing misuse. Uniform standards such as upper tether straps and lower anchorage systems (which allow seats virtually to be snapped in place) have the potential to make CSS installation a much simpler process, requiring very little instruction.
With respect to our testing methods, it needs to be noted that there are limitations inherent in the SMOG readability test. Many common words such as "vehicle," "serious," and "injury" were repeated often in virtually all of the instruction sets. Although some may argue that these 3-syllable words may be easily understood, testing procedures called for them to be counted in the SMOG tally. This most likely increased the overall grade level of the samples. However, it is doubtful that these words alone could account for a doubling of the sample’s reading level in comparison to what experts recommend.
Also, the SMOG score instructions specifically stated that hyphenated words count as 1 word. This is worth noting, because some manufacturers hyphenated the words "rear-facing" and "forward-facing," whereas others did not. This difference may have affected comparisons among manufacturers but would not explain the sample’s high mean readability level overall.
We achieved a high degree of interrater reliability when applying the SMOG testing method to our study sample ( = 0.80). As noted in previous literature, a exceeding 0.6 is considered to reflect a good level of agreement.30 Also, the test’s outcome did not seem to be overly sensitive to brand or model names.
Finally, this study also suggests some areas for potential future research. It would be valuable, for example, to evaluate the effectiveness of installation instruction sets. This could be done by taking people with no previous experience with CSSs, giving them instruction manuals, and noting the success rate of installation. A small-scale study of this type has already been performed in Canada31; however, it may be beneficial to repeat this work on a larger scale. It would also be of interest to determine whether an association exists between literacy and proper CSS installation and use and whether misuse patterns are associated with the readability of instruction sets.
Still, it seems advisable from our data that manufacturers of CSS rewrite their instruction sets to a fifth-grade reading level. This could be accomplished by using shorter sentences and simpler words. For example, "collision," "automobile," and "remedied" could be replaced by "crash," "car," and "fixed." Subsequent testing could verify whether the desired level of clarity had been achieved. The NHTSA has announced that they will consider mandating a minimum reading level for CSS labels and written instructions after conducting more research.32 Manufacturers and regulators may also want to explore whether alternatives to written installation instructions should be made available to consumers. If the above recommendations are put into practice in the short term and design improvements are widely adopted in the long-term, then the prevalence of proper CSS use may increase to a level befitting the importance of this effective injury prevention tool.
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ACKNOWLEDGMENTS |
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We acknowledge Susanne Ogaitis-Jones and Julia Alkire for sharing expertise on CSS, David Cruess for guidance on statistical analyses, and the NHTSA for making CSS instruction collection available and for providing valuable background information on this topic. Julianne J. Brown acted as our second rater of CSS instructions.
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FOOTNOTES |
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Received for publication Nov 13, 2001; Accepted Jul 22, 2002.
Reprint requests to (D.C.G.) Department of Preventive Medicine and Biometrics, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Rd, Bethesda, MD 20814. E-mail: dgirasek{at}usuhs.mil
The views expressed in this report are those of the authors and do not necessarily reflect those of the US government.
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PEDIATRICS (ISSN 1098-4275). ©2003 by the American Academy of Pediatrics
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