Anxious Apprentice & Loop Eradicator

Tantala

I have successfully completed the Anxious Apprentice quest and killed the dremora. This gave me the cheater defeater achievement but there is another associated achievement called loop eradicator. Am I right in assuming that to get this I need to actually prevent the experiment getting to the stage where the dremora appears? I'm asking because I don't want to waste a lot of time if I am barking up the wrong tree.

Thanks