Examining the Psychometric Properties and the Factor Structure of “Early Development Instrument” in Preschool Children Aged 4 to 6 Years in Mashhad with Rasch Model

Document Type : Original Article




The aim of this study was to determine the psychometric properties and factor structure of Early Development Instrument (EDI) in preschool children in Mashhad. The research method was descriptive cross-sectional survey. A sample of 456 children (226 girls and 230 boys) of preschool children (4 to 6 years old) in the academic year 2018-19 was selected by multi-stage random sampling method and their educators responded to the items of EDI. First, confirmatory factor analysis was performed using R software. The initial 5-factor model did not fit well enough with the data, so the whole sample was divided into two subsets of 228 people. Exploratory factor analysis was performed on the first subset and two items were excluded from the instrument. Then, confirmatory factor analysis was performed on the second subset, and the 5-factor model from exploratory factor analysis fit the data. Then, the parameters of the items were estimated by the Classical Test Theory, and all subscales had good reliability. Then, the fit of the items was estimated using the Partial Credit Model (PCM). After removing the inappropriate items, the reliability of the instrument was 0.97 and the PSI index was 0.95. There was also a difference between the average of girls and boys on all subscales. Also, the Differential Item Functioning (DIF) showed that 26 items have a differential function among girls and boys. Finally, a 93-item instrument with desirable psychometric properties has been developed for preschool children.


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