It was a pretty good mathematics application, I thought. If this was presented to a math class, how would the students react. My guess is that they would say the math failed. A 91% chance is not a sure thing, but there have been some studies that suggest people take it to be that. And on the other hand, people assume that a really low percentage is the same as no chance. This might lead to a good class discussion.
This made me think about other forecasts? Specifically, how do weather forecasters decide on the percent chance of rain. I found a post by a weather person at WESH TV, Amy Sweezey. Although we haven't met, and I don't even know what she looks like, she seems delightful. And smart. I learned some interesting things about how they make a percent estimation of rain for the day.
So what does a 40% chance of rain mean? It turns out that it depends.
Let's say that there is a 40% chance of rain over about half of the area in question.
Some weather forecasts will call this a 40% chance of rain. In a way it is. There is a 40% chance of rain somewhere in the area.
Some weather forecasts will call this situation a 20% chance of rain. And again in a way it is. There is a 20% chance that it will rain where you are currently standing.
As Amy says, "When it comes down to it, you cannot base your plans around a rain percentage." It's more important to know where, what time, and how heavy it will be.
It's because of this that many stations won't even do a percentage. Instead they might use descriptive words like "scattered showers", "isolated", "a few showers", and "likely".
