I studied applied mathematics and statistics both BSc & MSc. I taught myself electronics, with the help of online tutorials and a couple of good books. Little by little, reading here and there I have learned a lot. I've basically learned everything I know now (not that much) in just under two years.
I believe the science/math background helps you learn quicker, even if it isn't directly applicable. Building, let's say, a tube preamp requires nothing more than some simple algebra but learning how it all works, how to bias and figure out the operating points, etc, I think is where it helps a bit.
But Hagerman's kits don't require much knowledge as he has done all the work for you. You just need to know how to solder, which just takes a tiny bit of practice.