Marginal/Conditional probability

[refresh2039]

	sunny	rainy
hot	0.7	0.2
cold	0.4	0.6

t : weather is hot
v: it is rainy

Calculate the probability of p or q is true?

I've already calculated the marginal and conditional probabilities from the previous questions but on this question I don't understand what does "is true" mean? Can anybody point me in the right direction? What topic of probability is this?

 

[tkhunny]

You defined "t" and "v" and then asked a question of "p" and "q". Does that make sense?

It's either hot or it isn't. What's p(hot)?
It's either rainy or it isn't. What's p(rainy)?
What's p(hot AND rainy)?
What's p(hot OR rainy)?

Odd, though, 0.7+0.2+0.4+0.6 = 1.9 ?? Are these probabilities? Should this dispay specify a valid distribution?

 

[refresh2039]

Sorry I didn't copy the right values!

	sunny	rainy
hot	0.3	0.1
cold	0.1	0.5

t : weather is hot
v: it is rainy

Calculate the probability of t or v is true?

p(hot) = 0.4
p(rainy) = 0.6
p(hot AND rainy) = is it 0.4 * 0.6?
p(hot OR rainy) = 0.4 + 0.6 - 0.24?

 

[tkhunny]

Sorry I didn't copy the right values!

	sunny	rainy
hot	0.3	0.1
cold	0.1	0.5

t : weather is hot
v: it is rainy

Calculate the probability of t or v is true?

p(hot) = 0.4
p(rainy) = 0.6
p(hot AND rainy) = is it 0.4 * 0.6?
p(hot OR rainy) = 0.4 + 0.6 - 0.24?

??

It's an assignment in reading the table. Only addition is required.

But first, 0.4 + 0.6 = 1.0 -- Did you multiply where addition is indicated? Don't do that.


p(hot) = 0.3 + 0.1 = 0.4 Got it!
p(rainy) = 0.1 + 0.5 = 0.6 Got it.
p(hot AND rainy) = 0.1 -- Only one cell fits BOTH criteria.
p(hot OR rainy) = 0.3 + 0.1 + 0.5 = 0.9 -- Three cells meet EITHER criterion.