Intention-to-treat analysis (ITT)
A method of analysis for randomized trials in which all patients randomly assigned to one of the treatments are analysed together, regardless of whether or not they completed or received that treatment. This is complex area, and there are many definitions of what consitutes ITT.
Consider a typical migraine trial, in which patients are randomised in groups, given a tablet, and told to take it if they have a migraine. Some people have a migraine and take the tablet. Some do not have a migraine and do not take the tablet. Is the proper analysis on the number randomised, or the number ransomised and who actually had a migraine? There is no simple answer about what is correct.