Odds of rain in March

[LevHunter]

Hi TalkStats!

I have a problem that I was thinking you all might be able to help me with. I know that it typically rains 5 out of 31 days at a particular location. If I were to recalculate the odds for 2 more days, how would I do that?

Day one the odds would be 5/31, but I know it would not be 5/30 on the second day. I'm a bit rusty on my stats here.

 

[fed2]

if im reading you right the expected number of rain days over the next two days is (5/31)*2?

 

[LevHunter]

Basically I want to know the chances it will rain on either of those two days. So, on Monday what are the odds of rain? Based off if it rained or not on Monday, what are the odds it rains on that Tuesday?

This is given that the odds of rain on any particular day in the month of March at this location is 5/31.

 

[hlsmith]

If each day is an independent event then there is a 5/31 odds on everyday.

 

[LevHunter]

If each day is an independent event then there is a 5/31 odds on everyday.

What if I wanted to ask "what are the odds it rains either day in the next two days"?

 

[hlsmith]

I think prob for both would be multiplication and either is addition. But I am not 100% on the latter!!!

 

[fed2]

either would be 2*(5/31) - (5/31)^2 = 30%, ie by inclusion/exlcusion?

 

[lamchops]