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UBC Theses and Dissertations

A validity study of the dyslexia determination test (Griffin & Walton,1981) Simmons, William A. R.


Dyslexia has always been diagnosed by exclusion after an extensive battery of tests has eliminated all etiology. The Dyslexia Determination Test (D.D.T.) is an attempt to provide a direct diagnosis of dyslexia and to categorize the disability into various subgroups which may lead to more prescriptive remediation. The. purpose of this investigation was to study the validity of the D.D.T. by administering it to two distinct groups of readers (dyslexic and normal) to ascertain whether the test could discriminate between the two groups and further to examine the efficacy of the test's division of subjects into types of dyslexia as defined by the authors of the D.D.T. The sample taken from grades four to seven pupils in four Burnaby Schools, was comprised of two groups: a Control Group defined as average readers and an Experimental Group defined as at least two years below grade placement in reading with no known etiology. Groups were identified, based upon Canadian Tests of Basic Skills Vocabulary and Comprehension scores. Initial screening was done by conferencing with administrators, counsellors and teachers. Further screening was done with the Slosson Intelligence Test. A final sample of 14 Control and 14 Experimental subjects was identified. All were administered the D.D.T. by examiners who were not aware that the subjects comprised two groups. Results of the D. D. T. were analyzed by a discriminant analysis procedure. Scoring and analysis were also done by the examiners following the Manual procedures and guidelines. The discriminant analysis demonstrated that the D.D.T. was able to differentiate between the groups to a statistically significant level. Manual scoring and analysis resulted in few subjects being identified as dyslexic with no clear indicators of the types of dyslexia defined by the authors. One type of dyslexia was not indicated in any subject. Limitations of the study and the Test were noted and discussed. Suggestions were made for further research and for improvements to the Test, procedures and the Manuai.

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