I have been writing a research proposal. In a particular part of the proposal, I talk about statistical methods that will be used to avoid "overfitting." This is a statistical concept describing a situation in which a model is overly complex and therefore has low error but not because of real signal but because of the large number of variables in the model. (See Wikipedia link: https://en.wikipedia.org/wiki/Overfitting)
A friend commented that she thought it should be "over fitting". This is probably where the term "overfitting" came from.
I wanted to pose this question to the Stack Exchange English Language & Usage to get people's thoughts on the matter! Which spelling should it be, "over fitting" or "overfitting"?