It seems to be very basic static typing along the lines what Java or C has stashed on top an Smalltalkesque object-oriented language, so I am not surprised, the many years I used dynamically typed languages I maybe once or twice had a type error of the kind "confusing int with string" (e.g. when selecting a number from database and it being returned as string).
For the benefits of static typing I would rather look into something like Haskell which has a much stronger notion of type and builds many language features around this notion. It's probably harder to design a reasonable study comparing that with for example Smalltalk, though.
I'd be more interested in comparing Haskell to one of those even stronger typed programming languages. I'm forgetting the name of them, but it would be interesting to see how much is too much.
Are you thinking of Agda/Coq/Idris, which have dependent types? If you understand a bit of type theory, this is an interesting paper: http://www.cs.cmu.edu/~fp/papers/popl99.pdf
For the benefits of static typing I would rather look into something like Haskell which has a much stronger notion of type and builds many language features around this notion. It's probably harder to design a reasonable study comparing that with for example Smalltalk, though.