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2010-05-13, 08:51 AM (ISO 8601)
- Join Date
- Jul 2008
Calculating Probability: Did I get something wrong?
"It doesn't matter how much you struggle or strive,
You'll never get out of life alive,
So please kill yourself and save this land,
And your last mission is to spread my command,"
Slightly adapted quote from X-Fusion, Please Kill Yourself
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2010-05-13, 08:56 AM (ISO 8601)
- Join Date
- Jan 2006
- Gender
Re: Calculating Probability: Did I get something wrong?
The quote in your OP seems to link to a different thread/post than the one where this discussion actually took place. Can you give more context?
From what you've said, your calculation appears to be correct.
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2010-05-13, 09:03 AM (ISO 8601)
- Join Date
- Jul 2008
Re: Calculating Probability: Did I get something wrong?
I didn't think any more context was neccissary. The discussion was one of my all nighter arguments, this time reguarding the CR of Ekolids, here: http://www.giantitp.com/forums/showthread.php?t=151854
My origional claim is at the bottom of post 27."It doesn't matter how much you struggle or strive,
You'll never get out of life alive,
So please kill yourself and save this land,
And your last mission is to spread my command,"
Slightly adapted quote from X-Fusion, Please Kill Yourself
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2010-05-13, 09:03 AM (ISO 8601)
- Join Date
- Dec 2006
- Location
- Orlando, FL
- Gender
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2010-05-13, 09:05 AM (ISO 8601)
- Join Date
- Jul 2008
Re: Calculating Probability: Did I get something wrong?
"It doesn't matter how much you struggle or strive,
You'll never get out of life alive,
So please kill yourself and save this land,
And your last mission is to spread my command,"
Slightly adapted quote from X-Fusion, Please Kill Yourself
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2010-05-13, 09:13 AM (ISO 8601)
- Join Date
- Jan 2006
- Gender
Re: Calculating Probability: Did I get something wrong?
Whereas the obvious course of action to my eyes is to ask the guy who told you you were wrong why he thinks so. I thought you might have done so there and so I could take a look at his reasoning and see if I was missing something, but the point doesn't seem to have been followed up at all.
Perhaps he's referring to your wording, saying "you do X Y% of the time" instead of "you have a Y% probability of doing X". They're not the same thing, though the distinction isn't really important in this case.
But ultimately, we can't read Greenish's mind for you. If you want to know his reasoning, you'll have to ask him.
Incidentally, I think your math for the initiative is wrong. My calculation:
SpoilerHis modifier is +3, yours is +6. You win ties. Look at all the results he can get on a roll of 1-20. For each one, work out how many possible results on your own roll will equal or beat his. Add them up and convert to a total probability.
So if he rolls 20 for a result of 23, you can beat that with a result of 17+, which means 4 out of 20 results. If he rolls 19 you beat it on 5 results, and so on down to his rolling a 4 for a 7 which you automatically beat 20 out of 20 results; same for 3, 2, and 1. So if he has 20 different rolls and you have 20 possible results against each of them, that's 400 total rolls in which you succeed 20+20+20+20+19+18...+5+4 times. Comes out to 264 results in your favour, or 66% of the total.Last edited by kamikasei; 2010-05-13 at 09:27 AM.
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2010-05-13, 09:24 AM (ISO 8601)
- Join Date
- Jul 2008
Re: Calculating Probability: Did I get something wrong?
At first I just assumed I was wrong since maths never was my strong point, then after going over it several times and googling statistical probability I ask him in the last post to explain why I was wrong, but by then the discussion had died out.
Since I felt the issue was more about me than the origional discussion, I felt I should start a new thread rather than bumping that one, especially since it would require me to double post.
I guess it was my wording. Either that or they got confused with the common mistake of thinking that having gotten 2 heads in a row the probability of getting a third one is 1/8, when it is actually 1/2, and thought I was using the same flawed logic in my calculations."It doesn't matter how much you struggle or strive,
You'll never get out of life alive,
So please kill yourself and save this land,
And your last mission is to spread my command,"
Slightly adapted quote from X-Fusion, Please Kill Yourself
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2010-05-13, 09:29 AM (ISO 8601)
- Join Date
- Jan 2006
- Gender
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2010-05-13, 09:29 AM (ISO 8601)
- Join Date
- Apr 2010
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2010-05-13, 09:32 AM (ISO 8601)
- Join Date
- Jul 2008
Re: Calculating Probability: Did I get something wrong?
"It doesn't matter how much you struggle or strive,
You'll never get out of life alive,
So please kill yourself and save this land,
And your last mission is to spread my command,"
Slightly adapted quote from X-Fusion, Please Kill Yourself
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2010-05-13, 09:32 AM (ISO 8601)
- Join Date
- Jan 2006
- Gender
Re: Calculating Probability: Did I get something wrong?
If you want to predict three heads in a row, before any coins have been flipped, the probability is 1/8th (and the same for any other specific combination, for that matter). But once you've started flipping coins, the probability of each individual one coming up one way or another is unaffected by the flips that have come before. Getting "heads, heads, tails" is just as probable as getting "heads, heads, heads", after all.
(Or in other words: yes, right.)
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2010-05-13, 09:32 AM (ISO 8601)
- Join Date
- Mar 2009
Re: Calculating Probability: Did I get something wrong?
Yes, that's the gambler's fallacy.
http://en.wikipedia.org/wiki/Gambler%27s_fallacyBEEP.
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2010-05-13, 09:34 AM (ISO 8601)
- Join Date
- Feb 2010
- Location
- Finland
Re: Calculating Probability: Did I get something wrong?
Nah, it was just plain ol' fail at statistics on my part (I was pulling an allnighter too, and in the spirit of one-upsmanship I was also having a beer or two).
Quotes:Praise for avatar may be directed to Derjuin.Spoiler
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2010-05-13, 09:37 AM (ISO 8601)
- Join Date
- Dec 2006
- Location
- Ireland
Re: Calculating Probability: Did I get something wrong?
I'm curious: how did you calculate the probability of winning initiative to be 0.6?
For every winner, there are dozens of losers. Odds are that you're one of them.
We are here for the sake of others.
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2010-05-13, 09:40 AM (ISO 8601)
- Join Date
- Mar 2009
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2010-05-13, 09:42 AM (ISO 8601)
- Join Date
- Jul 2008
Re: Calculating Probability: Did I get something wrong?
"It doesn't matter how much you struggle or strive,
You'll never get out of life alive,
So please kill yourself and save this land,
And your last mission is to spread my command,"
Slightly adapted quote from X-Fusion, Please Kill Yourself
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2010-05-13, 09:45 AM (ISO 8601)
- Join Date
- Jan 2006
- Gender
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2010-05-13, 09:47 AM (ISO 8601)
- Join Date
- Dec 2006
- Location
- Orlando, FL
- Gender
Re: Calculating Probability: Did I get something wrong?
That was my question; assuming that you and someone else each roll d20, and you have some bonus advantage, you'll never have a 60% (exactly) chance of beating them.
I'm pretty sure that's not how it works.
If you look at all the possible combinations of rolls for various bonus advantages:
- p1 bonus advantage= 0, p1 beats p2 190 times, p2 beats p1 190 times, tie 20 times, P1 wins 47.50% of the time, ties 5% of the time
- p1 bonus advantage = 1, p1 beats p2 210 times, p2 beats p1 171 times, tie 19 times, P1 wins 52.50% of the time, ties 4.75% of the time
- p1 bonus advantage = 2, p1 beats p2 229 times, p2 beats p1 153 times, tie 18 times, P1 wins 57.25% of the time, ties 4.55% of the time
- p1 bonus advantage = 3, p1 beats p2 247 times, p2 beats p1 136 times, tie 17 times, P1 wins 61.75% of the time, ties 4.25% of the time
- p1 bonus advantage = 4, p1 beats p2 264 times, p2 beats p1 120 times, tie 16 times, P1 wins 66% of the time, ties 4% of the time
Last edited by Jayabalard; 2010-05-13 at 09:51 AM.
Kungaloosh!
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2010-05-13, 09:50 AM (ISO 8601)
- Join Date
- Dec 2006
- Location
- Ireland
Re: Calculating Probability: Did I get something wrong?
Would it not be 0.66? (I'm assuming the +6 modifier trumps the +3 if they tie.)
Edit: Oh, you actually simulated it. Nice.Last edited by Saeveo; 2010-05-13 at 09:53 AM.
For every winner, there are dozens of losers. Odds are that you're one of them.
We are here for the sake of others.
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2010-05-13, 09:54 AM (ISO 8601)
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- Jan 2006
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Re: Calculating Probability: Did I get something wrong?
It'd be 0.66 with the given figures. 0.6175 was for Boci's mistaken assumption of a 2-point difference. (Or maybe he was right on that and made a typo in the figures.)
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2010-05-13, 10:05 AM (ISO 8601)
- Join Date
- Dec 2006
- Location
- Ireland
Re: Calculating Probability: Did I get something wrong?
For every winner, there are dozens of losers. Odds are that you're one of them.
We are here for the sake of others.
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2010-05-13, 10:28 AM (ISO 8601)
- Join Date
- Feb 2010
- Location
- Finland
Re: Calculating Probability: Did I get something wrong?
The 18% figure is pretty irrelevant though, since if you win initiative and manage to hit (about 40% chance to do both), you'll get IF damage, so the last roll merely determines the amount.
If someone better versed on statistics than me wants to calculate it, I'd be happy to know the average damage of IF with +11 modifier.
For reference:{TABLE]score | bonus
10-14:| +1d6
15-19:| +2d6
20-24:| +3d6
25-29:| +4d6
30-34:| +5d6[/TABLE]Quotes:Praise for avatar may be directed to Derjuin.Spoiler
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2010-05-13, 12:18 PM (ISO 8601)
- Join Date
- Dec 2008
Re: Calculating Probability: Did I get something wrong?
1d20+11 IF
skill checks do not auto fail
1-3+11->12-14->+1d6
4-8+11->15-19->+2d6
9-13+11->20-24->+3d6
14-18+11->25-29->+4d6
19-20+11->30-34->+5d6
(3/20)x(1d6)->3d6/20
(5/20)x(2d6)->10d6/20
(5/20)x(3d6)->15d6/20
(5/20)x(4d6)->20d6/20
(2/20)x(5d6)->10d6/20
(3+10+15+20+10)(d6)(1/20)
(58/20)d6
2.9d6
or 2.9X3.5 average damage
10.15~10 damage"The fool is marked by ignoring the wisdom of the wise. The wise are marked by their eagerness to heed the wisdom of the fool."
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2010-05-13, 12:27 PM (ISO 8601)
- Join Date
- Sep 2009
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- Some corn field
- Gender
Re: Calculating Probability: Did I get something wrong?
If you win initiative, don't you catch them flatfooted in the first round? That would explain why both are 60%. therefore, it is. 30% chance, unless my orginal statement is wrong
Spoiler
In the past, I played Sir Theo Roost.
I am soon to begin playing his heir, Dora the Destroya
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2010-05-13, 12:40 PM (ISO 8601)
- Join Date
- Feb 2010
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- Finland
Re: Calculating Probability: Did I get something wrong?
Last edited by Greenish; 2010-05-13 at 12:40 PM.
Quotes:Praise for avatar may be directed to Derjuin.Spoiler