Quick Math Probability Help

[mike01]

Need some quick help, fellas. After I get the answer I'll let you guys in on what I am trying to figure out, pretty interesting stuff.

Event A has a 20% chance of happening.....If Event A happens, then event B has a 30% chance of happening. If event A does not happen, event B cannot happen.

What is the probability that both Event A and Event B happen????

I tried drawing a quick probability tree, and found 14 possible outcomes, with three out of fourteen ending up with both happening, for a 21% probability, but this seems very high.


Thoughts?

[JohnnytheSkin]

Re: Quick Math Probability Help

Wow, a statistics problem seven years removed from a collegiate stats course. Don't even know where to begin...


Sorry, can't help you.

[mgoblue]

Re: Quick Math Probability Help

Wow, a statistics problem seven years removed from a collegiate stats course. Don't even know where to begin...


Sorry, can't help you.

Ditto, though only 6 years here...ugh, I hate probablity, that stuff is brutal

[mike01]

Re: Quick Math Probability Help

Don't feel bad guys. I am 2/2 in failing stats classes in college so far. LOL, I am just a much more logical thinker than a math guy.

[mike01]

Re: Quick Math Probability Help

I think it is 6% now.....sounds about right.

Multiplying the probability that event B occurs, figuing event A has already occured, by the probability that Event A will occur...30% times 20% equals 6% I believe.

Would be good if someone could confirm though.

[PlayaHataSupreme]

Re: Quick Math Probability Help

I think it is 6% now.....sounds about right.

Multiplying the probability that event B occurs, figuing event A has already occured, by the probability that Event A will occur...30% times 20% equals 6% I believe.

Would be good if someone could confirm though.

That's the answer I calculated in my head before I looked at your answer......

You multiplied

.3 * .2 = .06.

So I'll say that's the answer.

[Bacardi151]

Re: Quick Math Probability Help

That's the answer I calculated in my head before I looked at your answer......

You multiplied

.3 * .2 = .06.

So I'll say that's the answer.

i believe you are correct


the probability of event A AND event B happening=
p(A and B) = p(A) * p(B).

god i hate stats, i am more of a discrete math dude; maybe cause its geared more towards programming logic.

[mike01]

Re: Quick Math Probability Help

thanks guys, I'm gonna roll with that answer. Here is an article I wrote about Barry Bonds and the HR chase, and how to hustle some cash.

Investing In Barry

So Barry Bonds is stuck on HR number 754 heading into a six game road trip with the Giants this week. They play in Los Angeles tonight, and that has everyone wondering; will Barry tie or break the record on the road? The reception if he does will likely be mixed. Some cheers for those who realize they witnessed serious history, and those who hate Bonds with a passion and claim he is a cheater. I'm no Bonds fan, but I may stand and clap politely if I was in attendance on the record breaking nights.

So I started thinking....how much are the next two home run balls going to be worth? Mark McGwire's record breaking 62nd home run went for an astonishing three million dollars. THREE MILLION. Of course, this was at a time when baseball was thriving and the single season home run chase was drawing in millions of fans as Sammy Sosa and McGwire battled it out chasing Roger Maris' 61. Funny how at that time, nobody cared about steroids. Anyway, three million for McGwire's ball. According to auction experts, Bonds' next two balls will likely go for quite a bit less. Maybe one million, max. Likely around $500,000 though. Still not too shabby for some lucky fan, right?

So what are your odds of catching one of these balls if Barry hits them in LA? Well, if you are sitting in the outfield, they may be better than you think. Looking at the LA Dodger seating chart, by my estimate, there are 250-300 fans in each seating section. Looking again, I count 13 full sections where the home run could legitimately be hit, including left center field and NOT including the top sections in the deep parts of the park. That means that there are really only 3,250 fans who have a good shot at this. There is also a big gap in center field for the hitters background, and thats worth at least another 750 seats. So, we'll round it out to 4,000 to make things easy. A one in 4,000 chance to catch Barry's home run ball if he hits one. OK, so that is less than a .001 chance, but still, not bad for your $30 ticket, right?

So you and your friends were thinking about buying up a few tickets and taking your chances in game one, eh? Let's take it a step farther....OK, a lot of steps farther.

People want to witness history, so what would they say to a free ticket to the Dodgers game tonight? If they are baseball fans, they would jump all over it. Even if they aren't fans of the game, they may accept and take a friend or give them away. Free seats for a chance to witness history. Why are these people getting free tickets? Because you are giving them away.

In fact, you aren't just giving tickets away, you are investing in Barry Bonds. The offer you make to people, is that you will buy their tickets (lets say, $30) for them, if they agree to sign over 90% of the rights to the home run ball if they happen to catch one hit by Barry. Hell, even if they catch it, they still come away with a free ticket to the game and $50,000. And chances are terrible that they will, so they still had a free ticket if they come away empty. So you only give this offer to one person, and your odds are still....terrible. But, what if you gave this offer to 100 people? 250? 500? 1000?????

If you found 1,000 men (because they will fight for the ball better than women, and there WILL be a fight) willing to accept your offer, and paid for all of their tickets, thats only $30,000. Barry hits a home run ball, and you have a 1/4 chance of catching it now, maybe slightly better considering 1/4 to 1/3 of the outfield will be kids and women. So you have a 30% chance at catching the home run ball if hit. You pay $30,000 to have a shot at $450,000.

Is this a good deal?

Well, you need to know the percentages of Barry hitting a home run to figure this out. He'll face right-handers Brad Penny and Brett Tomko, and lefty Mark Hendrickson on Wednesday. He has 2o HR in 249 ABs on the year in 91 games played. All games in LA are at night, so I expect him to play in all three. Going by HRs and games, he has a 22% chance to hit a HR every game he plays. If you factor in things like Dodger Stadium being a pitchers park, Penny being a monster on the mound, Tomko sucking, Barry pressing to get this over with, Barry feeding of the negative crowd, etc....I think it all evens out for the most part, so I'll stick with a 22% chance he hits a homer in each game of the LA series. Still with me?

How about you make this offer good for two games, the Penny game tonight and the Tomko game on Thursday. Therefore you could possibly hit the jackpot and catch BOTH 755 and 756. Spending a total of 60K to earn a possible 900K or more. Not exactly a good possibility, but a possibility none the less. And if you can't get both, you are still going for a shot to get either one of them by adding the Tomko game.

Taking this one game at a time though.....

If Barry has a 22% chance to hit a home run tonight (he has 3 career HR in 25 AB's vs Penny), and if you have a 30% chance of catching that ball if he does....what are the chances you catch a home run ball hit by Bonds tonight? Multiplying the probability that you catch the ball assuming Bonds hits a homer (30%) by the chance that Bonds hits a home run (22%) and you have a....6.5% of catching a Barry Bonds home run ball tonight with your 1000 men in the outfield bleachers.

So is spending $30,000 tonight worth a 6.5% chance at $450,000? There is quite a bit of math involved, but thanks to Stanford Wong's book, Sharp Sports Betting, he has a table of odds for us to look at and easily figure it out. Whew. Wong's table tells us that with an event that has a 6.5% chance of occurring, you need to be getting odds of AT LEAST +1438, or 14.38:1, to break even. What does laying $30,000 to win $450,000 give you in terms of odds? +1500, or 15:1

What does this mean?

Following this plan of buying tickets for 1,000 people in the outfield seats of Dodger Stadium, in the applicable 300's sections, in exchange for 90% of the rights to the home run ball that is caught is a slightly PROFITABLE investment. Meaning, if you did this same investment over and over again, in the long run you would come out with more money that you started with. Skeptical? Sure, this wasn't exactly rocket science, and a bit of it was quite subjective. Thirty dollars also might be a big low of a guess, since this is history we are talking about here, and tickets may well be going for $75. But if you can weasel your way into only giving up $30 per ticket, I think you have yourself a good investment. You may even be able to negotiate the 90% rights up to 95% or even 100%.

I would get into the math and facts for the series as a whole, but I have a plane to LA I need to catch.

[mgoblue]

Re: Quick Math Probability Help

i believe you are correct


the probability of event A AND event B happening=
p(A and B) = p(A) * p(B).

god i hate stats, i am more of a discrete math dude; maybe cause its geared more towards programming logic.

That's what I came up with after I posted...Figured 6% seemed about right, but I never fully had probability "click", i'm like you and more of a discrete math guy. As much as it pains me to say it (I'm having flashbacks right now), I'd probably rather have a dot moving along some crazy 3d path compared to probability questions.

[TheGamingChef]

Re: Quick Math Probability Help

It's not really that difficult if you think about it (which is the difficult part). The total probability is 30% of 20% - think of 10% of 20% (2%), and then multiply that by 3 (6%).

[JohnnytheSkin]

Re: Quick Math Probability Help

As much as it pains me to say it (I'm having flashbacks right now), I'd probably rather have a dot moving along some crazy 3d path compared to probability questions.

Unfortunately my five Calculus courses were much more interesting then my singular Statistics course...however dorky that sounds.

I much prefer differential equations and quantitative comparisons to probability questions.

Engineering FTW!

[TheMatrix31]

Re: Quick Math Probability Help

Math sucks in any and all forms.

[Blaxican8504]

Re: Quick Math Probability Help

Math sucks in any and all forms.

[Leon]

Re: Quick Math Probability Help

Math sucks in any and all forms.

Yes, but when you get it, it makes you feel all smart inside.



Even though a lot of people know how to do what you just did and you're just trying to make yourself feel special. True story.

[rudyjuly2]

Re: Quick Math Probability Help

Unfortunately my five Calculus courses were much more interesting then my singular Statistics course...however dorky that sounds.

I much prefer differential equations and quantitative comparisons to probability questions.

Engineering FTW!

Screw you engineers! Stats are great!!

I will say that I enjoyed the stats courses more than any other math courses in my time in university (got a math and stats degree). Queuing theory and risk management were also interesting to go along with probability theory.