17
Designing the Comprehensive Diagnostic Test of Dyslexia (CDTD) and Investigating its
Validity and Reliability for Primary School Students of Isfahan in 2015-2016 Heidari Kh1, Faramarzi S2, Abedi A2, Ghamarani A3
Abstract
Purpose: there is no standard reading test for elementary school grades (first to six) in Iran to
early identify students with special problems in reading. Considering the large population of
individuals with reading problems and the urgent need for rapid and accurate diagnosis, the
present study aimed to designing the Comprehensive Diagnostic Test of Dyslexia (CDTD) and
investigating its validity and reliability for primary school students.
Methods: This was a cross-sectional instrument development study. The statistical population
of the study included all primary school students with in all the six educational regions of
Isfahan in the academic year of 2015-2016. The sample was selected by stratified random
sampling in proportion to the population size. Accordingly, 600 students (300 girls and 300
boys) were selected from the six grades. To develop the Comprehensive Diagnostic Test of
Dyslexia (CDTD), after reviewing the previous studies and the theoretical literature, books and
existing tests, the most important components of dyslexia were extracted through thematic
analysis and the early version of CDTD was developed. Content validity was investigated by
Lawshe method and for convergent validity, the correlation between CDTD and reading and
dyslexia test was estimated. The internal consistency was estimated by Cronbach’s alpha
coefficient and the validity of the test was estimated by the test-retest method.
Results: the minimum and maximum Content Validity Ratio (CVR) for CDTD were 0.33 and
1, respectively and the Content Validity Index (CVI) was 0.81. The correlation between CDTD
and the reading and dyslexia test was .56 (p=0.004). There was a statistically significant
difference between students with and without reading difficulties in CDTD (p=0.001). The
internal consistency of CDTD was 0.75 and the Intraclass Correlation Coefficient (ICC) was
.88.
Conclusion: the results of the analysis revealed that the CDTD is properly valid and reliable.
Therefore, this test can be used to develop the profiles, and finding the strengths, and
weaknesses of students with dyslexia and it can also be used for educational and rehabilitation
purposes.
Received: 2018.02.22 Accepted: 2018.09.18
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