There should be a link right there on the page, that you could click, and give it your credit card, and then you could leave a tip.
Yeah, I know it was already pointed out, but you know, sometimes enough is not enough.
Your sample has two traits: you know them, and they are engineers.
How do you know which trait to attribute your observations to?
Maybe the real correlation is not with their education, but their willingness to share some of their views with you.