Parametric analyses of summative scores may lead to conflicting inferences when comparing groups: a simulation study

Khan, Asaduzzaman, Chien, Chi-Wen and Bagraith, Karl S. (2015) Parametric analyses of summative scores may lead to conflicting inferences when comparing groups: a simulation study. Journal of Rehabilitation Medicine, 47 4: 300-304. doi:10.2340/16501977-1941

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Author Khan, Asaduzzaman
Chien, Chi-Wen
Bagraith, Karl S.
Title Parametric analyses of summative scores may lead to conflicting inferences when comparing groups: a simulation study
Journal name Journal of Rehabilitation Medicine   Check publisher's open access policy
ISSN 1650-1977
1651-2081
Publication date 2015-04
Year available 2015
Sub-type Article (original research)
DOI 10.2340/16501977-1941
Open Access Status File (Publisher version)
Volume 47
Issue 4
Start page 300
End page 304
Total pages 5
Place of publication Uppsala, Sweden
Publisher Foundation for Rehabilitation Information
Collection year 2016
Language eng
Formatted abstract
OBJECTIVE: To investigate whether using a parametric statistic in comparing groups leads to different conclusions when using summative scores from rating scales compared with using their corresponding Rasch-based measures.

METHODS: A Monte Carlo simulation study was designed to examine between-group differences in the change scores derived from summative scores from rating scales, and those derived from their corresponding Rasch-based measures, using 1-way analysis of variance. The degree of inconsistency between the 2 scoring approaches (i.e. summative and Rasch-based) was examined, using varying sample sizes, scale difficulties and person ability conditions.

RESULTS: This simulation study revealed scaling artefacts that could arise from using summative scores rather than Rasch-based measures for determining the changes between groups. The group differences in the change scores were statistically significant for summative scores under all test conditions and sample size scenarios. However, none of the group differences in the change scores were significant when using the corresponding Rasch-based measures.

CONCLUSION: This study raises questions about the validity of the inference on group differences of summative score changes in parametric analyses. Moreover, it provides a rationale for the use of Rasch-based measures, which can allow valid parametric analyses of rating scale data.
Keyword Rating scales
Parametric statistics
Rasch analysis
Simulation
Summative scores
Rasch-based measures
Construct validity
Ordinal scales
Rasch analysis
Rating scales
Statistics
Outcomes
Designs
Model
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2016 Collection
School of Human Movement and Nutrition Sciences Publications
 
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