My potential Masters advisor seems very interested in taking me on as a student since my first email to him was 5 days ago and he is already discussing which project to do with me. He said he aims to work on a project with his grad students that will help them with their future goals. He mentioned one direction I could go with a project. However, it requires a lot of math and statistics. I actually enjoy statistics and what he's proposing sounds very interesting, however, I am worried I don't have the knowledge to take on this project. I took 2 stats courses in undergrad and he has my transcript. I will also be taking 2-3 more stats courses in my masters. These courses will be more applicable to this field. It would be much easier to find a project for me to do if I go with the way that he's proposing. How do I raise my concerns to him? What should I say?
First thing, in a master or in a PhD, you are a student and it's normal to learn new things. If your potential advisor wanted someone for this project that already knew how to do it, he/she would hire a postdoc. Actually, learning new techniques, in statistic or other, is what every scientist do, during their entire career.
Second, you are already planning on taking additional statistical courses and your potential advisor knows your background. It seems to me that you will be fine and that you can do this. This sounds a lot like impostor syndrom and you should read on that. In that case, I wouldn't talk about that to a potential advisor. Do talk about it if you need to, but preferably to professional help or people who know you. For the record, I wouldn't hesitate in talking about impostor syndrom with my advisor, but I know him, he knows me and we have an healthy mentor-mentee relationship...
If you still want to touch the subject with your potentiel advisor, do it simply:
I'm very interested in this project, but I'm worried I don't currently have to knowledge to do it. Are those courses sufficent to help me with the project? Will there be additional help available ?
This is the good moment to enquire about lab resource, which can be professional statistical help or colleagues. Good luck.
Just be honest about your worries but also show that you are motivated. For example, you could go along the lines of
The project sounds really interesting, but I am not yet an expert on topic XX. Can you suggest a textbook to work through or a course to take before starting my work with you? How long do you assume it will take to get the necessary knowledge? Is there someone from your team (e.g. another student) who knows more about it, would it be possible to put us in the same office?
Just show that you are willing to fill the gaps you still have, ask for advice on how to best do it and you should be ok. Learning new stuff and getting the knowledge needed to do a project is part of your task during a Masters after all.