Do I need An Umbrella?
Do I need an Umbrella?
On a local UK broadcaster’s website, there’s a weather page which has postings like this:
But what does “25% chance of rain” mean? After all, there’s an “areal” doubt (where in NW4, which is a postal district in London) and a “temporal” doubt (when in that hour) and a “volume” doubt (how much rain represents a threat to my clothing).
The 25% looks to be the “risked mean” of the input variables, so:
- Does it mean there’s a 100% chance that a quarter of NW4 will get rain in that hour?
2. Does it mean there’s a 100% chance that all of NW4 will get rain but for only a given 15 minute period?
3. Does it mean there’s a 50% chance that half of NW4 will get rain in that hour?
4. If I happen to be somewhere in NW4 does it mean that I have a 25% chance of getting wet?
And how much rain is enough to get you wet?
In “hydrocarbon reserves speak” the volume doubt can be treated as the “economic minimum” but the remaining question can be phrased as “can the areal doubt or the temporal doubt be represented as the risk or the uncertainty of getting wet”? – or are the two doubts inseparable as sub-elements of the risk and there is no “uncertainty”?
Which of the quoted scenarios should you use before deciding whether to take an umbrella, always remembering the universal truth in the General Law of Umbrellas, that if you take one it will be sunny, if you don’t you get soaked.
Also, do we need to consider what the time of the day means:
The question is: are these chances dependent or independent? In other words, if I’m out there at 12 and I get wet, does this change the chance of getting wet later on?
If not, the chance of rain sometime during the 6 hours is 93% – grab your umbrella. But if they are linked, then the chance is less.
What is the chance that it will rain between 12:00 and 18:00? Or between 12:00 and 15:00?) Have a guess and email us at firstname.lastname@example.org with your answers and we’ll tell you if you are right.
Our REP (Reserves Evaluation Program) application allows you to set a variety of risking schemes (based on such elements as Reservoir presence/Seal effectiveness etc.) and a variety of Probability Density Function shapes ( including Beta/Normal/Lognormal/ user-defined) to calculate the P10/P50/P90 levels) as well as the economic minimum.
There is also a comprehensive consolidation module that allows a company portfolio to be “rolled up” from all the company assets – and to work out, correctly, the chance that it will rain between 12:00 and 18:00.
To see what’s available why not try downloading a copy of REP from www.logicomep.com/products/REP and start a free month’s trial.
Image source: Pixabay