Comparisons against baseline within randomised groups are often used and can be highly misleading

BACKGROUND: In randomised trials, rather than comparing randomised groups directly some researchers carry out a significance test comparing a baseline with a final measurement separately in each group. METHODS: We give several examples where this has been done. We use simulation to demonstrate that...

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Detalles Bibliográficos
Autores principales: Bland, J Martin, Altman, Douglas G
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2011
Materias:
Methodology
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3286439/
https://www.ncbi.nlm.nih.gov/pubmed/22192231
http://dx.doi.org/10.1186/1745-6215-12-264
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author Bland, J Martin
Altman, Douglas G
author_facet Bland, J Martin
Altman, Douglas G
author_sort Bland, J Martin
collection PubMed
description BACKGROUND: In randomised trials, rather than comparing randomised groups directly some researchers carry out a significance test comparing a baseline with a final measurement separately in each group. METHODS: We give several examples where this has been done. We use simulation to demonstrate that the procedure is invalid and also show this algebraically. RESULTS: This approach is biased and invalid, producing conclusions which are, potentially, highly misleading. The actual alpha level of this procedure can be as high as 0.50 for two groups and 0.75 for three. CONCLUSIONS: Randomised groups should be compared directly by two-sample methods and separate tests against baseline are highly misleading.
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spelling pubmed-32864392012-02-25 Comparisons against baseline within randomised groups are often used and can be highly misleading Bland, J Martin Altman, Douglas G Trials Methodology BACKGROUND: In randomised trials, rather than comparing randomised groups directly some researchers carry out a significance test comparing a baseline with a final measurement separately in each group. METHODS: We give several examples where this has been done. We use simulation to demonstrate that the procedure is invalid and also show this algebraically. RESULTS: This approach is biased and invalid, producing conclusions which are, potentially, highly misleading. The actual alpha level of this procedure can be as high as 0.50 for two groups and 0.75 for three. CONCLUSIONS: Randomised groups should be compared directly by two-sample methods and separate tests against baseline are highly misleading. BioMed Central 2011-12-22 /pmc/articles/PMC3286439/ /pubmed/22192231 http://dx.doi.org/10.1186/1745-6215-12-264 Text en Copyright ©2011 Bland and Altman; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
spellingShingle Methodology
Bland, J Martin
Altman, Douglas G
Comparisons against baseline within randomised groups are often used and can be highly misleading
title Comparisons against baseline within randomised groups are often used and can be highly misleading
title_full Comparisons against baseline within randomised groups are often used and can be highly misleading
title_fullStr Comparisons against baseline within randomised groups are often used and can be highly misleading
title_full_unstemmed Comparisons against baseline within randomised groups are often used and can be highly misleading
title_short Comparisons against baseline within randomised groups are often used and can be highly misleading
title_sort comparisons against baseline within randomised groups are often used and can be highly misleading
topic Methodology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3286439/
https://www.ncbi.nlm.nih.gov/pubmed/22192231
http://dx.doi.org/10.1186/1745-6215-12-264
work_keys_str_mv AT blandjmartin comparisonsagainstbaselinewithinrandomisedgroupsareoftenusedandcanbehighlymisleading
AT altmandouglasg comparisonsagainstbaselinewithinrandomisedgroupsareoftenusedandcanbehighlymisleading

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