Reliability of the Test of Integrated Language and Literacy Skills (TILLS)

Marja Liisa Mailend, Elena Plante, Michele A. Anderson, E. Brooks Applegate, Nickola W. Nelson

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Background: As new standardized tests become commercially available, it is critical that clinicians have access to the information about a test's psychometric properties, including aspects of reliability. Aims: The purpose of the three studies reported in this article was to investigate the reliability of a new test, the Test of Integrated Language and Literacy Skills (TILLS), with consideration of both internal and external sources of measurement error. Methods & Procedures: The TILLS was administered to children aged 6;0–18;11 years. The participants varied in terms of their language and literacy skills and included children with typical language development as well as those diagnosed with language or learning disability. The sample of children also varied in terms of their racial and socioeconomic backgrounds. Study 1 (N = 1056) assessed the internal consistency of TILLS calculating the coefficient omega for each subtest. Study 2 (N = 103) and Study 3 (N = 39) used the intra-class correlation coefficients to report on test–retest and inter-rater reliability respectively. Outcomes & Results: The results indicate strong internal consistency and inter-rater reliability for all subtests of TILLS. The test–retest reliability was strong for all but one subtest, for which the intra-class correlation coefficient was in the acceptable range. Conclusion & Implications: This article provides clinicians with essential scientific information that supports the internal and external reliability of a new test of oral and written language skills, the TILLS. Information about reliability is critical for guiding the selection of an appropriate diagnostic tool amongst a number of options.

Original languageEnglish (US)
Pages (from-to)447-459
Number of pages13
JournalInternational Journal of Language and Communication Disorders
Issue number4
StatePublished - Jul 1 2016


  • children
  • language skills
  • literacy skills
  • psychometrics
  • reliability

ASJC Scopus subject areas

  • Language and Linguistics
  • Linguistics and Language
  • Speech and Hearing


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