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With a clustered randomized design require a sample size almost seven times as large as that of the clinical trials using the traditional individual randomization. Two commonly encountered mistakes in most cluster randomized trials are given below 1. Although the trials adopt a cluster randomization, the analysis of data completely ignores this fact and uses subject as the unit of analysis. 2. Sample size estimation fails to take into consideration the variance inflation factor. The first...

Goals Of Clinical Trials

The ultimate goal of clinical research is to obtain an unbiased inference with possibly best precision in order to scientifically address the clinical questions regarding the study drug under investigation with respect to a target patient population. As indicated by Lachin 2000 , the meaning of an unbiased trial is two-fold. First, the estimated treatment effect between the investigational drug and a control is unbiased. Second, the statistical testing procedure for detecting a treatment effect...

Parallel Group Designs

A parallel group design is a complete randomized design in which each patient receives one and only one treatment in a random fashion. Basically there are two types of parallel group design for comparative clinical trials, namely, group comparison or parallel-group designs and matched pairs parallel designs. The simplest group comparison parallel group design is the two-group parallel design which compares two treatments e.g., a treatment group vs. a control group . Each treatment group...

Bias And Variability

As was indicated earlier, the FDA requires that the results from clinical trials be accurate and reliable in order to provide a valid and unbiased assessment of true efficacy and safety of the study medication. The accuracy and reliability are usually referred to as the closeness and the degree of the closeness of the clinical results to the true value regarding the targeted patient population. The accuracy and reliability can be assessed by the bias and variability of the primary clinical...