Hi Fady,

You made a very excellent point because there is definitely a greater chance of data distortion if too many centers are present. Variability needs to be controlled and in order to do so, the scope of the study needs to be clearly defined and those who are conducting the study in the center (operators) need to be trained properly because they are the ones who gather data. A test method that is capable of being conducted in different centers should be created and the operators should be closely monitored in order to reduce variation. However, since repeatability and reproducibility of data is important in a study, companies prefer to have multiple centers because they want to see how different operators handle the study. As Luisa and other students mentioned, the line should be drawn when an appropriate amount of operators at the center are present to properly conduct the study.