How can i tell if the masters have been moved to Aperture. I think when i first opened aperture the application asked me if i wanted to move the iPhoto library and i said yes but i don't recall the question of moving the masters or not.
They would have been moved into the Aperture library unless you specified that they not be in Aperture's Preferences.
One way to check is to select an image and then see if "Show if Finder" is availiabe in the File menu. If it is, you can see where the file is stored, if it isn't, the file is in the Aperture library and you can delete the version in iPhoto.
Of course you could always back up the iPhoto version to DVD just to have one more backup. More is better when it comes to backups.
I opened iPhoto highlighted a picture and looked under the file menu. There was no "Show if Finder" choice only "Show Aperture library". This then means that that the masters from iPhoto are now part of the Aperture library?