Hi,

I have a question regarding probability. I know most people here enjoy math and not only computers - seeing as they go hand in hand. And I wanted to know if I was correct in my guess.

Say you have two independent events. Event 1 and Event 2. The chance that Event 1 occurs is .03 and the chance for Event 2 is .35. My assumption is that the likely hood of them both occurring is .03*.35. Where I'm getting stumped how often would they occur per year, assuming each event will happen once per day. Would it be .03*.35*365?

Thanks

# Probability Question

Page 1 of 1## 2 Replies - 1180 Views - Last Post: 22 November 2009 - 10:29 PM

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**Replies To:** Probability Question

### #2

## Re: Probability Question

Posted 22 November 2009 - 08:42 PM

Yes, but only if you were to simply ask, what is the expected number of days with joint events.

This is where things get funky. Each event

Quote

assuming each event will happen once per day

*doesn't*happen once per day. Right? There's a probability of the event happening.### #3

## Re: Probability Question

Posted 22 November 2009 - 10:29 PM

tshauck, on 22 Nov, 2009 - 03:03 PM, said:

Would it be .03*.35*365?

No, as that would result in a value greater than 1.

To figure out the chance of something happening at least once over a specified duration, you need to come at it backwards.

The chance that both events will happen in a day = 0.03 * 0.35 = 0.0105

The chance both events don't happen in a day = 1 - 0.0105 = 0.9895

The chance that both events don't happen in a day, for multiple days = 0.9895^# of days = 0.9895^365 = 0.021221

The chance that both events will happen in a day, at least once, in a year = 1 - 0.021221 = 0.978779

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