Clinical Studies means clinical research trials, where bio-equivalent study is done means analytical results are compared for a new medicine (Test) with old medicine having same content(Reference).
In clinical trial there could be number of clinical trial phase in which dosing of medicine is done, and blood samples are taken in different time slots, sample may be 15 to 30.
You are given every care and food with other facilities like T.V,Carr-om,Chess etc. for your time pass for the period you are in the Lab.
But for being eligible for any clinical study/Clinical Research you must be pass in Screening.