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Sample size and statistical conclusions from tests of fit to the Rasch measurement model according to the RUMM2030 program
Kristianstad University, Research Environment PRO-CARE. Kristianstad University, School of Health and Society, Avdelningen för Hälsovetenskap I. Kristianstad University, Research Platform for Collaboration for Health.ORCID iD: 0000-0003-2174-372X
Kristianstad University, Research Environment PRO-CARE. Kristianstad University, School of Health and Society, Avdelningen för Hälsovetenskap I.ORCID iD: 0000-0003-4820-6203
2015 (English)Conference paper, Oral presentation only (Refereed)
Abstract [en]

Sample size is a major contributor to statistical null hypothesis testing, which is the basis for many approaches to testing Rasch model fit. To allow for taking this into account, the RUMM2030 Rasch analysis software has the ability to adjust n in the calculation of its chi-2 based fit statistics. This paper examines the effects of such post-hoc adjustments on the statistical conclusions, and explores the occurrence of type I errors with Rasch model fit statistics implemented in RUMM2030. Data simulations of Rasch model fitting 25-item dichotomous scales with sample sizes ranging from n=50-2500 were generated an analysed regarding fit with and without adjusted sample sizes corresponding to the same n values as those simulated. Results suggest that post-hoc downward sample size adjustment is a useful procedure to avoid type I errors when working with relatively large data sets (n≥500). The value of upward adjustment with small data sets is less clear, particularly regarding the total item-trait chi-2 test, which tends to falsely signal misfit. Under the assumption of Rasch model fit, our observations suggest that a sample size around 250 (up to about 500) provides a good balance for the statistical interpretation of RUMM2030 fit statistics.

Place, publisher, year, edition, pages
2015.
Keyword [en]
Fit statistics, RUMM2030, simulation study
National Category
Health Sciences
Identifiers
URN: urn:nbn:se:hkr:diva-14576OAI: oai:DiVA.org:hkr-14576DiVA: diva2:854542
Conference
The 4th International Outcome Measurement Conference, IOMC 2015, Chicago, IL, USA
Available from: 2015-09-17 Created: 2015-09-17 Last updated: 2016-01-05Bibliographically approved

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http://jampress.org/iomc2015.htm

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Hagell, PeterWestergren, Albert
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CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf