My first blog post of this calendar year. I've made some changes, such as stepping down from my administrative position at the university. That means I'm on sabbatical this year, or as the provost calls it, "time off for good behavior." I could get used to this, but just as soon as I do, it'll be over.
Anyway, I've noticed a subtle change to the Weather Channel app on my phone. Here's a screenshot:
Notice anything unusual? What does it mean to say there's a 14% chance of rain? Or a 30% chance? Or a 90% chance?
I've been noticing a lot of statistical misinterpretation lately. Malaysian Airlines has two accidents in the span of a week (one of them not their fault, to be sure) and people stop booking flights. If only everyone knew about Poisson processes...
But what's up with the Weather Channel? I'm sure they think that putting more exact percentages, like 47% at 5:00 pm, will inspire confidence. "Wow, they must be getting really good at forecasting!" I ask again: what does it mean to say there's a 30% chance of rain? It really means that over time, looking at instances where similar atmospheric conditions were in place, it rained about 30% of the time. That's all. Reporting such a percentage to one more significant digit does not make me think it's a more reliable forecast, because weather is much too complicated for an accurate forecast more than a few minutes into the future (maybe a couple of hours). After that, the possible trajectories from the given initial conditions may diverge too wildly to make an accurate prediction.
So, nice try, Weather Channel, but I'm not convinced. I've never taken a 20% chance or rain as a serious threat, so I'm not about to consider a 22% chance any other way.