13.41 Traffic, running late, and bias: A friend tells you that there is a correlation between how late she’s running and the amount of traffic. Whenever she’s going somewhere and she’s behind schedule, there’s a lot of traffic. And when she has plenty of time, the traffic is sparser. She tells you that this happens no matter what time of day she’s traveling or where she’s going. She concludes that she’s cursed with respect to traffic.

a. Explain to your friend how other phenomena, such as coincidence, superstition, and the confirmation bias (Chapter 5), might explain her conclusion.

b. How could she quantify the relation between these two variables: the degree to which she is late and the amount of traffic? In your answer, be sure to explain how you might operationalize these variables. Of course, they could be operationalized in many different ways.

c. Let’s say your friend tries to quantify her bad luck and examines a range of associations between pairs of variables. She finds a correlation between the amount of time she has to spend outside on a given day and the amount of precipitation on that day. Why might this be a spurious correlation?