Single word test for the assessment of speech sound production in Persian speaking children: Development, validity and reliability.

Objectives: Single word tests are used frequently to determine clients' speech sound errors. These tools are user-friendly and popular for speech and language pathologists. The aim of this study was to design and validate a single word test for the assessment of speech sound production for Persian speaking children.

Methods: The present study included two phases. In phase I, test material was developed. Psychometric properties were evaluated in phase II. In the next phase, 525 typically developing Persian-speaking children with the age range of 3-5 years old were studied. Statistical Package for the Social Sciences, version 24.0 (SPSS, Inc., Chicago, IL) was used for statistical analysis of this study. The significance level was set at (p < 0.05). Pilot study was performed by administrating the test on 25 typically developing children, construct validity: by administrating the test on 400 typically developing children and the comparison of performance of the children in 4 age groups (discriminative validity regarding age and by administration of this test and phonetic subtest of Persian version of diagnostic evaluation of articulation and phonology on 100 children (convergent validity)). Inter-rater reliability was performed by transcription and scoring of samples of 25 children and calculation of Intra Correlation Coefficient (ICC) was calculated. Test-retest was completed by administrating the test two times on 30 children with two weeks intervals. Internal consistency was achieved by the calculation of the correlation of the items of test.

Results: The final version of the test includes 70 target words for assessment of the consonants in three positions, vowels in medial position and consonant clusters (CVCC). There was 80% or more than it for the percentage agreement between experts for the content validity. There wasn't any significant difference between experts' responses about items of the test. 4 pictures were revised based on children's responses for the pilot study. All of the reliability values (test-re test, internal consistency and inter-rater reliability) were higher than 0.85. There was a significant difference between the four age groups for the mean value of Persian single word test for speech sound production (p < 0.0001). There was a high correlation between the score of this instrument and the scores of participants in the Phonetic sub-test of the Persian version of Diagnostic evaluation of articulation and phonology(r = 0.934, p < 0.0001).

Conclusion: It seems that the Persian Speech sound Production Test is a reliable and valid tool that can be used to measure speech sound errors for Persian speaking children.