Comment by sweettea
3 years ago
Expected value is already what most forecasts show. Expected value conveys information poorly in some common cases, like thunderstorms in the summer. It is very different to hear there's a 20% chance of a thunderstorm, dropping an inch of rain, vs. a 100% chance of .2" rain - the former needs a backup plan to deal with rain, the latter needs to plan for rain. Hence I prefer the text forecasts from the NWS, which list an amount possible, plus more in thunderstorms, rather than a bare number.
Meanwhile the 'probability' listed in forecasts is also well defined as an expected value - it's (probability of X% rain coverage) * (X %), over all X. (Rain is defined as > .01")
Okay, in very high variance cases like thunderstorms the expected value might indeed not be enough, but there are usually additional storm warnings for that anyway. My claim is just that the expected amount of rainfall is much more interesting than the probability of rainfall. Yet the apps I know display probabilities prominently, not expected values.