What random assignment does and does not do

Random assignment of patients to comparison groups stochastically tends, with increasing sample size or number of experiment replications, to minimize the confounding of treatment outcome differences by the effects of differences among these groups in unknown/unmeasured patient characteristics. To w...

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Bibliographic Details
Published in:Journal of clinical psychology 2003-07, Vol.59 (7), p.751-766
Main Authors: Krause, Merton S., Howard, Kenneth I.
Format: Article
Language:English
Subjects:
Biological and medical sciences
Causality
Clinical trials
Confounding Factors (Epidemiology)
Experiments
Humans
Medical sciences
Methodology. Experimentation
Observer Variation
Psychology
Psychology. Psychoanalysis. Psychiatry
Psychopathology. Psychiatry
Psychotherapy
Random Allocation
Randomized Controlled Trials as Topic - methods
Randomized Controlled Trials as Topic - statistics & numerical data
Reproducibility of Results
Selection Bias
Stochastic Processes
Techniques and methods
Treatment Outcome
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Summary:Random assignment of patients to comparison groups stochastically tends, with increasing sample size or number of experiment replications, to minimize the confounding of treatment outcome differences by the effects of differences among these groups in unknown/unmeasured patient characteristics. To what degree such confounding is actually avoided we cannot know unless we have validly measured these patient variables, but completely avoiding it is quite unlikely. Even if this confounding were completely avoided, confounding by unmeasured Patient Variable × Treatment Variable interactions remains a possibility. And the causal power of the confounding variables is no less important for internal validity than the degree of confounding. © 2003 Wiley Periodicals, Inc. J Clin Psychol.
ISSN:0021-9762
1097-4679
DOI:10.1002/jclp.10170