# Probability of Occurance

#### Shiner452

##### New Member
Hi I'm new to probability and need help with what is probably a simple equation for you guys.

I am trying to calculate the probability of even A occurring when 1 or more conditions are true.

When Condition 1 is true Event A happens 22% of the time.
When Condition 2 is true Event A happens 34% of the time.
When Condition 3 is true Event A happens 51% of the time.

What is the probability of Event A happening if Conditions 1, 2, and 3 are all true?
What is the probability of Event A happening if only Conditions 1 and 3 are true?

How do I write this formula?

Thanks!

Aaron

#### heidir1224

##### New Member
Hello Aaron!

I am learning myself but would you use the multiplication rule for this?
P(A) + P(B) + P(C) - P(AandB) - P(AandC) - P(BandC)

#### Shiner452

##### New Member
I'm not sure I follow. How do I calculate that?

Can you show me that mathematically?

#### dthiaw

##### New Member
Hi I'm new to probability and need help with what is probably a simple equation for you guys.

I am trying to calculate the probability of even A occurring when 1 or more conditions are true.

When Condition 1 is true Event A happens 22% of the time.
When Condition 2 is true Event A happens 34% of the time.
When Condition 3 is true Event A happens 51% of the time.

What is the probability of Event A happening if Conditions 1, 2, and 3 are all true?
What is the probability of Event A happening if only Conditions 1 and 3 are true?

How do I write this formula?

Thanks!

Aaron
try Baye's theorem