Trial size design and study population

A clinical trial must obviously have a control group, against which the test (intervention) group can be compared. The control group may receive (a) no intervention at all (b) a placebo (i.e. a 

The size of the trial will be limited by a number of factors, including  

Whereas a comprehensive phase III trial would normally require at least several hundred patients, smaller trials would suffice if, for example  

Choosing the study population is obviously critical to adequate trial design. The specific criteria of patient eligibility should be clearly predefined as part of the primary question the trial strives to answer. 

Cross-over trial design Factorial design Hybrid design Large simple clinical trials 

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