Author Topic: Another statistical question  (Read 488 times)

Another statistical question
« on: March 20, 2020, 08:17:38 am »
Checking the weather this morning to see if worth putting washing out. 10% chance of rain most the day.

Iirc that means the chance of it raining all those ten hours is tiny so 0.00000000001 or maybe a zero less or extra

But is the chance of it raining in one of 10 hours 100%

Re: Another statistical question
« Reply #1 on: March 20, 2020, 08:32:17 am »
No. Chance of it not raining at all is 35%.

If the probability of it raining in any given hour is 0.1, then the probability of it not raining in that hour is 0.9.

So the probability of not raining in 10 hours is 0.9^10 = 0.35.

This of course ignores conditional probabilities, such as if it rains in one hour, the probability of it raining in the next hour may no longer be 10%.

Another statistical question
« Reply #2 on: March 20, 2020, 09:48:25 am »
Weather in a particular hour is not a discrete independent event.

Taking this to extreme, there is a 10% chance I will do a 200km Audax tomorrow. There is a 10% chance I will be doing Audax in each of the 10 hours from 8am.

The chance of me not audaxing at any point in the 10 hours is 90% and not 35%

The real answer is if you put your washing out it is guaranteed to rain. If you don’t it is guaranteed sunshine.
 


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Nelson Longflap

  • Riding a bike is meant to be easy ...
Re: Another statistical question
« Reply #3 on: March 20, 2020, 10:04:54 am »
The weather forecast is always right. If there's a 10% chance of rain and it rains, they were right. If there's a 10% chance of rain and it doesn't rain, they were right.  ;D
The worst thing you can do for your health is NOT ride a bike

Re: Another statistical question
« Reply #4 on: March 20, 2020, 02:20:39 pm »
This was covered in a recent BBC More or Less programme. Apparently, all it means is that given current weather conditions (temperature, wind, cloud cover etc), historical data shows that it rained 10 times out of a hundred in the time period quoted - hour or day, usually.
I am often asked, what does YOAV stand for? It stands for Yoav On A Velo