Rgarding experimental studies, in a randomized controlled trial (RCT) all are true, EXCEPT:

In randomized controlled trial, some losses to follow-up are inevitable due to factors, such as death, migration and loss of interest. This is known as attrition. If the attrition is substantial, it may be difficult to generalize the results of the study to the reference population. Every effo, therefore should be made to minimize the losses to follow-up. Ref: Park's Textbook of Preventive and Social medicine, 19th edition, Page 76-78.