Becoming a Data Head

CHAPTER 13Watch Out for Pitfalls

“The first principle is that you must not fool yourself, and you are the easiest person to fool.”

Richard P. Feynman, Nobel Prize-winning Physicist

Thinking, speaking, and understanding data is—in many ways—about knowing what mistakes can happen if you don't have your wits about you when working with and interpreting data. Some pitfalls will be easy to fix, but they're hard to find if you don't know where to look. And if you're not careful, they can turn into major data disasters like those introduced throughout this book (think Challenger and the 2008 housing market collapse).

Our goal in this chapter is to remind you of the pitfalls you've learned about and introduce you to a handful of other common pitfalls that, if you're not careful, can derail your work or (worse) convince you of something that isn't so.

Before we begin, let's take a moment to acknowledge that it's easy to complain about others’ mistakes. And we admit, data pitfalls and blunders are fun to discuss. While we encourage you to cast a skeptical eye on the work completed in your industry, let's also realize that change comes through empathy and encouragement. Honest mistakes happen, and to be sure, your authors came by the knowledge in this chapter the hard way. Thus, let's acknowledge that most of the pitfalls have no nefarious intent or bad faith behind them. Many are likely caused by people simply not knowing what can go wrong. This chapter brings those issues to the surface. ...