There are many factors to consider when using the multi-center form of clinical study. With this type of study, there could be variations between populations in their genetic makeup, cultural backgrounds, and environmental settings. This could affect comparison of results received from different locations. When doing multi-center trials, it is important to take these factors into consideration when performing the study. It is better to have multi-center trials be done in a common area to keep the differences at a minimum. There is no way to determine exactly how many centers is too much and will decrease variability. The number of centers is based on the study being done and how in depth the results are being analyzed. With more centers, there is more reliability in the results. However, this may result in less number of patients being studied.