Sorry, wasn't clear enough on the "human behavior" bit. Where data scientists are dealing with business problems, you can pretty much always assume that the dat

Sorry, wasn't clear enough on the "human behavior" bit. Where data scientists are dealing with business problems, you can pretty much always assume that the data describes human behavior at least in part. Doubly so if you're talking about data that's big enough to not be processable on a single computer, and also needs to be handled in short order, since that implies we're in Big Data (emphasis on the capital B and D) territory. The counter-hypothetical you're giving just isn't plausible for the situation at hand. Analyzing bird songs on the Galapagos is scientist work, not data scientist work. Analyzing bird songs in an urban area might more plausibly be data scientist work, in that it gets you back toward business applications, but also gets us back into a spot where there's no way you could just assume there's no day-of-week effect. I'm gonna stand firm on that one. That sort of thing is worrisome - I don't care if it's someone who holds a PhD or someone who just took a MOOC or two, data scientists have a professional responsibility to be way less sloppy than that.