# proabability

• Oct 11th 2012, 12:04 PM
tukker0509
proabability
The probability of an event and its complement equals one. True or false?
• Oct 11th 2012, 12:31 PM
Plato
Re: proabability
Quote:

Originally Posted by tukker0509
The probability of an event and its complement equals one. True or false?

$\displaystyle \mathcal{P}(E)+\mathcal{P}(E^c)=\mathcal{P}(E)+[1-\mathcal{P}(E)]=~?$
• Oct 11th 2012, 12:50 PM
jsweston828
Re: proabability
Quote:

Originally Posted by Plato
$\displaystyle \mathcal{P}(E)+\mathcal{P}(E^c)=\mathcal{P}(E)+[1-\mathcal{P}(E)]=~?$

What is that equation????!
• Oct 11th 2012, 01:19 PM
Plato
Re: proabability
Quote:

Originally Posted by jsweston828
What is that equation????!

Does the OP mean

$\displaystyle \mathcal{P}(E)+\mathcal{P}(E^c)$ OR $\displaystyle \mathcal{P}(E\cap E^c)~?$
• Oct 11th 2012, 01:20 PM
jsweston828
Re: proabability
Im so confused! I just answered True!!
• Oct 11th 2012, 01:23 PM
Plato
Re: proabability
Quote:

Originally Posted by jsweston828
Im so confused! I just answered True!!

Well $\displaystyle \mathcal{P}(E)+\mathcal{P}(E^c)=1$ AND $\displaystyle \mathcal{P}(E\cap E^c)=0.$
• Oct 11th 2012, 01:27 PM
jsweston828
Re: proabability
So would you say the answer is true or false!!
• Oct 11th 2012, 01:33 PM
Plato
Re: proabability
Quote:

Originally Posted by jsweston828
So would you say the answer is true or false!!

I have no idea. "The probability of an event and its complement equals one."
That is such a poorly constructed phrase as to be meaningless.
Look at reply #4. It could be either.
• Oct 11th 2012, 01:34 PM
jsweston828
Re: proabability
ohhh I see! Im just going to hope its correct!