Conditional Probability - Techist - Tech Forum

 Techist - Tech Forum Conditional Probability

 10-08-2018, 11:01 AM #1 (permalink) Super Techie     Join Date: Aug 2012 Location: UK Posts: 317 Conditional Probability Whelp, I have no idea where to put this, and even less of an idea whether anyone here can help me, so here goes nothing: Studying for my Advanced AI module, and I thought "Hey, let's do some of the questions from the textbook! They can't be much harder...". I then proceeded to cry myself to sleep. Basically, this question asks: And this is the answer they give: All I don't understand is, where does the ' A ^ ' go, on the 3rd step? It just disappears and I can't think of any logical reason why Any help will be forever loved and appreciated __________________ __________________ I have too many rubber ducks. Send help.
 10-08-2018, 01:34 PM #2 (permalink) True Techie   Join Date: May 2011 Location: SC Posts: 248 Re: Conditional Probability There is nothing here, but the question. The links or images you put in are not present. __________________ __________________
Super Techie

Join Date: Aug 2012
Location: UK
Posts: 317
Re: Conditional Probability

Quote:
 Originally Posted by bpm55 There is nothing here, but the question. The links or images you put in are not present.
That's odd, it works fine for me on my desktop and on my phone, can anyone else see it?
__________________
I have too many rubber ducks. Send help.

 10-09-2018, 08:35 AM #4 (permalink) Private Joker     Join Date: Feb 2007 Location: South Dakota Posts: 24,796 Re: Conditional Probability I can see them just fine. That said, I have no idea. Been a while since I've taken statistics or Logic, Sets, & Proofs . __________________ Laptop: MSI GT70 2OC-059us | i7-4700MQ | 16GB | GTX 770m | 500GB SSD / 750GB HDD | 17.3" | Win10 Pro Desktop: 4690k | 12GB g.Skill RipJaws | GTX 970 | 520hx | Z87X-UD4H | Corsair Vengeance C70 | Corsair H110 | Acer 25" | Acer 22" | Win10 Mobile: Google Pixel XL If I help you, or you just like what I said, rep me by clicking the under my post
 10-09-2018, 08:37 AM #5 (permalink) AR ML AI <3   Join Date: Dec 2006 Location: England Posts: 8,721 Re: Conditional Probability From what I remember Soulphire is alright at maths, he might be able to help. Other than that you might want to try https://math.stackexchange.com/ or the math subreddit https://www.reddit.com/r/math/ __________________ AMD Ryzen 2700X Corsair RGB Pro 16GB DDR4 3200Mhz EVGA RTX 2080Ti FTW3 Ultra WD Blue 250GB SSD / WD Blue M2 500GB SSD / SanDisk 240GB SSD / Samsung 860 EVO 1TB SSD WD Black 2TB HDD Asus Crosshair VII Hero X470 Seasonic 860w Platinum PSU Corsair 750D ATX Tower Sony Bravia X900F 49" 4K HDR Monitor
Super Techie

Join Date: Aug 2012
Location: UK
Posts: 317
Re: Conditional Probability

Quote:
 Originally Posted by kmanmx From what I remember Soulphire is alright at maths, he might be able to help. Other than that you might want to try https://math.stackexchange.com/ or the math subreddit https://www.reddit.com/r/math/
I thought it might be a long shot, worth asking though, some clever people here 😂
__________________

 10-09-2018, 07:09 PM #7 (permalink) True Techie   Join Date: May 2011 Location: SC Posts: 248 Re: Conditional Probability Good news is I can see the question. Bad news I have forgotten most of that math class. Sorry hopefully someone else can help out. __________________
 10-11-2018, 07:21 AM #8 (permalink) Lord Techie     Join Date: Mar 2007 Location: Australia Posts: 9,089 Re: Conditional Probability They just performed a simplification, the probability set of A in union with (B in union with A) is the same no matter how many times you say "in union with A", i.e. you can simplify it down to just B union A. That's why they say that bit about "and the fact that A union A == A" __________________ "As a result of all this hardship, dirt, thirst, and wombats, you would expect Australians to be a sour lot. Instead, they are genial, jolly, cheerful, and always willing to share a kind word with a stranger, unless they are an American." -- Douglas Adams
Super Techie

Join Date: Aug 2012
Location: UK
Posts: 317
Re: Conditional Probability

Quote:
 Originally Posted by S0ULphIRE They just performed a simplification, the probability set of A in union with (B in union with A) is the same no matter how many times you say "in union with A"
But isn't the probability of A ^ B the probability that both will happen at the same time? So wouldn't it be the probability of A happening on its own, plus the probability of both happening at the same time?

Thanks for helping btw, my lecturer for this module has no idea
__________________
I have too many rubber ducks. Send help.

Lord Techie

Join Date: Mar 2007
Location: Australia
Posts: 9,089
Re: Conditional Probability

Quote:
 But isn't the probability of A ^ B the probability that both will happen at the same time
Yep! Try making two overlapping circles, label A and B. Label the middle overlapping bit A^B

What is the probability that some random point I choose will be in set A^B (the tiny oval in the middle) AND in set A?
Well, set A^B is ENTIRELY within set A. So if it's in set A^B at all, it will 100% be in set A as well. We don't need to calculate that.

Or to state it more clearly, if we have P ( A ^ ( A ^ B)) then the associative law says we can also rewrite that as P((A ^ A) ^ B)
P(A ^ A) = P(A)

Also nice! Which AI course are you doing?
__________________

__________________
"As a result of all this hardship, dirt, thirst, and wombats, you would expect Australians to be a sour lot. Instead, they are genial, jolly, cheerful, and always willing to share a kind word with a stranger, unless they are an American." -- Douglas Adams

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post thosegiants Microsoft Windows and Software 2 03-31-2015 10:43 AM bargielml Microsoft Windows and Software 0 09-10-2014 09:37 AM murdocsvan Programming 9 12-14-2010 11:15 AM

#### Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

#### Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities