Sample Size and Power Calculation

What is "sample size" for a clinical study?
The sample size of a randomized controlled trial (RCT) is the number of subjects that are to be included in the study. This number determines the likelihood of detecting a certain magnitude of difference between treatment groups we usually assume that there will be a benefit from the new treatment. We can either vary the likelihood of detecting the difference (the power of the study) or the magnitude of the difference that we are trying to detect (the expected treatment effect).
How many patients do we need.

Three approaches for sample sized calculation:
(1) Statistical approach
How many needed to get firm evidence of treatment difference, if one exists?
(2) Economic approach
How many patients are available?
How much time, effort & cost is involved?
(3) Ethical approach
How soon can we stop the trial to avoid some patients getting inferior treatment?
More about the sample size calculation can be found here.

• The sample size is the most important determinant of the statistical power of a study, and a study with inadequate power is unethical unless being conducted as a safety and feasibility study.
  
• However, the calculation of sample size is not an exact science. It is therefore important to make realistic and well-researched assumptions before choosing an appropriate sample size.
  
• This sample size should account for dropouts

If you are in need of help with a sample size and power calculation, please e-mail us at: dmar@dmargroup.com