Jack:
Interesting work and area...
This work seems to be centered in around the Java programming language and large team participation.
One question I have been exploring is the application context for different programming languages.
For example Java, C++, Python and Ruby are very different computing languages.
Java and C++ are usually associated with large scale commercial systems.
Python and Ruby are usually associated with independent developers and small team start up organizations.
PHP appears to fit in between these two computer language groups.
The computing context is changing fast and computer languages like Go and Javascript are having a significant impact.
It appears to me that programming skills are strongly language dependent and would need to be measured using some type of real computer language and real problem set. The results may well vary between languages and application context.
Take care and have fun,
Joe