This is not a SAS related question. Refer your question to an appropriate forum.
As a brief overview, a Clinical Trial has to have a Protocol. The protocol describes all of the procedures, tests, data capture, reasoning etc. the encompasses everything in the trial. Once the trial is underway certain unavoidable or unintentional things may happen which means the actual event deviates from what it written in the protocol. This constitutes a Protocol Deviation. These deviations may be minor - leading to maybe small exclusions from the end product or major, leading to the whole subject data being excluded from analysis or from populations. Generally these feed directly into the Per Protocol Population.
You can find further information at CDISC website - the standards you should be using. Further information can be found on the PHUSE website.
