Understanding type I and type II errors, statistical power and sample size

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The results of a clinical trial may be subject to random error because of the variability in the measured data, which arises purely by chance. There are two types of random error – type I error and type II error. In this study, type I and type II errors are explained, and the important concepts of statistical power and sample size estimation are discussed.


The most important way of minimising random errors is to ensure adequate sample size; that is, a sufficient large number of patients should be recruited for the study.

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