Objective Studies?

There seem to be endless debates across the internet whether a "power conditioner" (I always conjure a soapy head image when I say that) is a genuine need or just so much snake oil for the gullible in the audiophile community.  There appears to be at least some consistency that concerns about power conditioners should be near the bottom of the audiophile's to-do list.  Yet there are some who claim, vociferously, that power conditions make a huge difference in sound quality.  And so the debate rages on....

What would seem to be helpful is an objective/scientific study regarding measurable differences they can make, if any.  Surely someone has done a valid study of the issue?  I'm hoping to avoid yet another power conditioner turf battle on Audiogon by focusing this post just on whether objective/scientific studies have been done.  If you know of any please share!