Strengths and Difficulties Questionnaire: internal validity and reliability for New Zealand preschoolers

Paula Kersten, Alain Vandal, Hinemoa Elder, Kathryn McPherson

Research output: Contribution to journalArticle

Abstract

Objectives: This observational study examines the internal construct validity, internal consistency and cross-informant reliability of the Strengths and Difficulties Questionnaire (SDQ) in a New Zealand pre-school population across four ethnicity strata (New Zealand European, Māori, Pasifika, Asian). Design: Rasch analysis was employed to examine internal validity on a subsample of 1,000 children. Internal consistency (n=29,075) and cross-informant reliability (n=17,006) was examined using correlations, intraclass correlation coefficients and Cronbach's Alpha on the sample available for such analyses. Setting & participants: Data were utilised from a national SDQ database provided by the funder, pertaining to New Zealand domiciled children aged 4 and 5, and scored by their parents and teachers. Results: The five subscales do not fit the Rasch model (as indicated by the overall fit statistics); contain items that are biased (differential item functioning) by key variables, suffer from a floor and ceiling effect and have unacceptable internal consistency. After dealing with differential item functioning the Total Difficulty scale does fit the Rasch model and has good internal consistency. Parent/teacher inter-rater reliability was unacceptably low for all subscales. Conclusion: The five SDQ subscales are not valid and not suitable for use in their own right in New Zealand. We have provided a conversion table for the Total Difficulty scale, which takes account of bias by ethnic group. Clinicians should use this conversion table in order to reconcile differential item functioning by culture in final scores. It is advisable to use both parents and teachers' feedback when considering children's needs for referral of further assessment. Future work should examine whether validity is impacted by different language versions used in the same country.
Original languageEnglish
JournalBMJ Open
Volume8
Issue number4
DOIs
Publication statusPublished - 21 Apr 2018

Bibliographical note

© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted. This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/

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