The tech intern data was a self-reported online survey distributed around tech-focused Facebook groups (eg: I definitely saw and participated in this survey last year, on Hackathon Hackers).

The other salary data was from "BLS May 2015 National Occupational Employment and Wage Estimates".

I found the survey useful to compare your offers to other offers at that company/ones nearby. It was way easier to use than glassdoor, especially because the offers increase a little every year and you want to be sure you're not getting screwed somehow.

Definitely should be used for any real analysis though, not even blog-post analysis.

They're skewed by the fact that the top companies are in higher CoL areas. Then again there are lower paying companies in these locations too.