Here's the data file they used. The University of Phoenix only has 72 data points. https://s3.amazonaws.com/ed-college-choice-public/Most+Recen...

I can't find anything about methodology other than the fact that only students who receive federal financial aid may be included.

I'll guess the data is skewed because University of Phoenix caters to people who are already working. Work experience + degree is better than just a degree.

I suspect that all state universities in locations that have cheaper cost of living that the national average (Texas, for instance) are hampered by viewing the data in the way it is being shown.

As a Texas Tech grad, I'm not that shocked.