User blog comment:John Lee Gamma Guild Team Vi Hart/Why Some People Didn't Get Invited to the Energy Points Challenge/@comment-29331244-20140905034238/@comment-24808864-20140905143441

I just ran some quick numbers too. It appears as though around 60% of our rather small sample size is receiving the invite. Because of the small sample, this might indicate that "half the people in KA" are receiving invitiations to test run this process.

That would be a reasonable way to randomly select participants, especially if half were solo and half were in teams.

I will run some more stats tests, and try to determine a confidence interval for the proportion of people that are being selected so that we might learn more about this "test run" process that KA is employing.