Think what is feasible and you will be amazed what is probable.
From the TV show 'Doc'
• If it's green or wiggles, it's biology
• If it stinks, it's chemistry
• If it does not work, it's physics
• If it's people-gazing, it's epidemiology
• If it has nothing to do with those nasty and pesky numbers, it's qualitative research
• If it's all business, it's health economics
• If it justifies perpetuating other people's mistakes, it's evidence-based medicine
(Partly from a variety of sources)