FacebookTwitter
Hatrack River Forum   
my profile login | search | faq | forum home

  next oldest topic   next newest topic
» Hatrack River Forum » Active Forums » Books, Films, Food and Culture » How do i determine average probability? (Page 1)

  This topic comprises 3 pages: 1  2  3   
Author Topic: How do i determine average probability?
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
Say I roll 20 d6's, what the "average" number I am likely to get? The Monster manual lists the average hitpoints for monsters but lets say I want to increase its HD or decrease it, how do i recalculate the average?
IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
If you don't know by now how to calculate an expectation value, you might as well give up on programming and go be a plumber or something. Come on, dude, this is first-year stuff. (First year of high school, that is.) Write a program to simulate it, you might learn something.
Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
fugu13
Member
Member # 2859

 - posted      Profile for fugu13   Email fugu13         Edit/Delete Post 
The average number you are likely to get for 20 die rolls is just 20 times the average number you are likely to get for one die roll, which is the value of each possible roll times the probability of that roll.

So, for one die roll the average is:

1/6 + 2/6 + 3/6 + 4/6 + 5/6 + 6/6 = 3.5

Alternatively, you could note that there are three pairs of numbers on the die that each add up to 7, therefore the average must be 3.5

So, the average number you will get for 20 die rolls is 70.

Posts: 15770 | Registered: Dec 2001  |  IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
I don't think you're doing anyone any favours by explaining this truly elementary stuff, fugu.
Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
fugu13
Member
Member # 2859

 - posted      Profile for fugu13   Email fugu13         Edit/Delete Post 
Eh, even without really basic math like this he could end up being an okay member of an application programming team. Not a game programmer, certainly.
Posts: 15770 | Registered: Dec 2001  |  IP: Logged | Report this post to a Moderator
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
quote:
Originally posted by King of Men:
I don't think you're doing anyone any favours by explaining this truly elementary stuff, fugu.

Even if it is elementary stuff I haven't had a statistics class to deal with probability in roughly 4 years. Its math, not algorithm design.
IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
Statistics? Dude, this isn't statistics, this is counting on yer dang fingers. This is two steps up from plain multiplication. Next you'll tell me you use a calculator for 7*8 on the grounds that you haven't studied multiplication in ten years. If you can't retain this much information from that class four years ago, you might as well give up on classes altogether; they're not doing you any good.
Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
BlackBlade
Member
Member # 8376

 - posted      Profile for BlackBlade   Email BlackBlade         Edit/Delete Post 
Don't be so hard on him KOM. Blayne if you really care about programming though, you're going to have to take some extra time out of your day to understand basic math. Maybe retake college algebra even if it doesn't go towards your major.
Posts: 14316 | Registered: Jul 2005  |  IP: Logged | Report this post to a Moderator
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
quote:
Originally posted by King of Men:
Statistics? Dude, this isn't statistics, this is counting on yer dang fingers. This is two steps up from plain multiplication. Next you'll tell me you use a calculator for 7*8 on the grounds that you haven't studied multiplication in ten years. If you can't retain this much information from that class four years ago, you might as well give up on classes altogether; they're not doing you any good.

I actually never learned my multiplication tables.

To clarify, I know MOST of them by now through day-to-day operations.But if Im at my computer, I use my calculator out of laziness.

IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
*Throws hands in the air, rolls eyes*

Really now. I must say my sympathy for your father is increasing with your every post.

Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
The White Whale
Member
Member # 6594

 - posted      Profile for The White Whale           Edit/Delete Post 
It takes very little time to learn to do simple multiplication in your head, and from that point on you save time and energy every time you see 7x8. You should see that, have the answer, and move on without blinking an eye.

You're attending school, now, right? I know most of my math and computer classes didn't allow calculators in the tests. Sure, the math was relatively simple, but you were absolutely expected to be able to do it without a calculator without a problem.

Posts: 1711 | Registered: Jun 2004  |  IP: Logged | Report this post to a Moderator
scifibum
Member
Member # 7625

 - posted      Profile for scifibum   Email scifibum         Edit/Delete Post 
quote:
Originally posted by Blayne Bradley:
quote:
Originally posted by King of Men:
I don't think you're doing anyone any favours by explaining this truly elementary stuff, fugu.

Even if it is elementary stuff I haven't had a statistics class to deal with probability in roughly 4 years. Its math, not algorithm design.
How would you write an algorithm to answer the question you started the thread with?
Posts: 4287 | Registered: Mar 2005  |  IP: Logged | Report this post to a Moderator
BlackBlade
Member
Member # 8376

 - posted      Profile for BlackBlade   Email BlackBlade         Edit/Delete Post 
quote:
Originally posted by Blayne Bradley:
quote:
Originally posted by King of Men:
Statistics? Dude, this isn't statistics, this is counting on yer dang fingers. This is two steps up from plain multiplication. Next you'll tell me you use a calculator for 7*8 on the grounds that you haven't studied multiplication in ten years. If you can't retain this much information from that class four years ago, you might as well give up on classes altogether; they're not doing you any good.

I actually never learned my multiplication tables.

To clarify, I know MOST of them by now through day-to-day operations.But if Im at my computer, I use my calculator out of laziness.

Nobody learns their multiplication tables without making a concerted effort to do so. It's extremely obnoxious to learn them, but I've yet to hear anybody memorize them and complain that they did not provide a return on their investment.

If you sit down and memorize at least your 2-12 tables you will find thousands if not millions of calculations you make the rest of your life will be much easier.

You probably won't take my advice Blayne, but it's there for you anyway.

Posts: 14316 | Registered: Jul 2005  |  IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
code:
10 GOSUB POST_ON_HATRACK
20 GOSUB WHINGE_ABOUT_HOW_HARD_STUFF_IS
30 GOSUB COMPLAIN_ABOUT_OTHER_PEOPLE
40 GOTO 10


Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
What have you got against the one-times table, BlackBlade? [Big Grin]
Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
BlackBlade
Member
Member # 8376

 - posted      Profile for BlackBlade   Email BlackBlade         Edit/Delete Post 
quote:
Originally posted by King of Men:
What have you got against the one-times table, BlackBlade? [Big Grin]

Everyone knows I am, if nothing else, a two timer.

In third grade my mom made me sit in a chair and start memorizing those freaking tables and I remember the laminated chart she gave me had the one table. The deal was every week I had to memorize three tables. I tried to pawn the one table off as one of those three, but no dice. I don't think my parents repeated the process with any of my 4 younger siblings, or heck my older sister for that matter.

Posts: 14316 | Registered: Jul 2005  |  IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
Didn't you learn it in school?
Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
BlackBlade
Member
Member # 8376

 - posted      Profile for BlackBlade   Email BlackBlade         Edit/Delete Post 
quote:
Originally posted by King of Men:
Didn't you learn it in school?

I don't recall there being a concerted effort to learn them in my two schools growing up. But with all the multiplication you had to accomplish through rote repetition you would have been royally screwed if you didn't memorize them.
Posts: 14316 | Registered: Jul 2005  |  IP: Logged | Report this post to a Moderator
Lisa
Member
Member # 8384

 - posted      Profile for Lisa   Email Lisa         Edit/Delete Post 
Blayne, just guess. If you guess a sufficiently large number of times, you're bound to get the answer correct.
Posts: 12266 | Registered: Jul 2005  |  IP: Logged | Report this post to a Moderator
HollowEarth
Member
Member # 2586

 - posted      Profile for HollowEarth   Email HollowEarth         Edit/Delete Post 
quote:
Originally posted by scifibum:
How would you write an algorithm to answer the question you started the thread with?

in matlab:

code:
r = ceil(6.*rand(20,1e4));
mean_of_20_d6 = mean(sum(r));

Basically, just generate many (above I used 10,000) groups of 20 random integers between 1 and 6, then add up each group and take the mean of the entire ensemble.

Incidently, I found 70.056 when I ran the above.

The outcome of this kind of experiment is precisely what we mean when we ask this kind of question, even if in general there are better ways to find the answer.

Posts: 1621 | Registered: Oct 2001  |  IP: Logged | Report this post to a Moderator
scifibum
Member
Member # 7625

 - posted      Profile for scifibum   Email scifibum         Edit/Delete Post 
HollowEarth: I wasn't really asking because I wanted to know. I was asking because I wanted Blayne to think about it.

Simulating the die rolls may be a perfectly valid way to approximate the answer, and it's good to know how to do that, but I did want to point out that it might often be easier and more efficient to know how to use mathematical functions to calculate that sort of thing than it is to simulate the experiment.

Matlab apparently makes it quite easy either way.

Posts: 4287 | Registered: Mar 2005  |  IP: Logged | Report this post to a Moderator
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
Yeah, Hollow, KoM, I didn't want to know the CODE to simulate the die roll as frankly there's billions of such things on the net, I wanted to know the theory behind figuring out averages so I could oddball in my head the average rather then thinking the average was always roughly half of the die rolled.
IP: Logged | Report this post to a Moderator
swbarnes2
Member
Member # 10225

 - posted      Profile for swbarnes2           Edit/Delete Post 
The "theory" is that since all the dice rolls are independant of each other, you can find the average for one, and just multiply for the number of dice you've got.
Posts: 575 | Registered: Feb 2007  |  IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
I know. Asking about the code might have been halfway reasonable. Not knowing the theory is epic-level ignorance (*). That's the point at which you should realise that you should drop what you're doing and go study po-mo feminism instead, where being utterly ignorant of your subject isn't a handicap.


(*) Or so I thought until you admitted to not knowing the multiplication tables.

Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
Paul Goldner
Member
Member # 1910

 - posted      Profile for Paul Goldner   Email Paul Goldner         Edit/Delete Post 
Seriously, Blayne, there's no way you can have a successful career in anything using mathematics if you don't know how to do averages at this point in your life. What you're asking for help on is stuff I had mastered before moving to middle school, and never had to think about it again. Its time to change career plans... or devote about 12 hours a day, every day, to catching up in your education.
Posts: 4112 | Registered: May 2001  |  IP: Logged | Report this post to a Moderator
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
quote:
Originally posted by King of Men:
I know. Asking about the code might have been halfway reasonable. Not knowing the theory is epic-level ignorance (*). That's the point at which you should realise that you should drop what you're doing and go study po-mo feminism instead, where being utterly ignorant of your subject isn't a handicap.


(*) Or so I thought until you admitted to not knowing the multiplication tables.

Yeah keep insulting the one guy who genuinely wants you to survive attacks from Britannia, keep doing that and see where it goes.
IP: Logged | Report this post to a Moderator
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
quote:
Originally posted by Paul Goldner:
Seriously, Blayne, there's no way you can have a successful career in anything using mathematics if you don't know how to do averages at this point in your life. What you're asking for help on is stuff I had mastered before moving to middle school, and never had to think about it again. Its time to change career plans... or devote about 12 hours a day, every day, to catching up in your education.

I hardly remember even so much as a single day of my youth in either high school or elementary school, its all frankly a blurr I retained I think the majority of my skills but I don't remember so much as a single day of it.

For the record I passed Calculus with 80% which to my knowledge is pretty much a requirement for programming physics or anything involving rates of change so obviously I'm not getting everything wrong.

IP: Logged | Report this post to a Moderator
Paul Goldner
Member
Member # 1910

 - posted      Profile for Paul Goldner   Email Paul Goldner         Edit/Delete Post 
Passing a class and understanding the material are different things.

You don't understand very simple math.

Posts: 4112 | Registered: May 2001  |  IP: Logged | Report this post to a Moderator
Tstorm
Member
Member # 1871

 - posted      Profile for Tstorm   Email Tstorm         Edit/Delete Post 
I remember learning multiplication tables starting in second grade. Some of them, we learned the pattern, and some of them, we learned by singing to a nursery rhyme. It's amazing that I can still remember the song to which we learned the 4 table.

I must admit to being flabbergasted that some people never learned the multiplication tables in school. (As in, it was never taught, not that they 'decided not to learn them'.) Seriously, what else should be taught in the elementary levels, math-wise?

Posts: 1813 | Registered: Apr 2001  |  IP: Logged | Report this post to a Moderator
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
quote:
Originally posted by Paul Goldner:
Passing a class and understanding the material are different things.

You don't understand very simple math.

And I perfectly understand college level calculus up to related rates, we didnt go into anti derivatives or integration but I roughly know what those are and understand pretty well everything before that.

Passing a class is different from understanding it but passing WELL is a far cry removed from just passing and requires understanding the material.

IP: Logged | Report this post to a Moderator
TomDavidson
Member
Member # 124

 - posted      Profile for TomDavidson   Email TomDavidson         Edit/Delete Post 
What's "passing well?" Is that a B+?
Posts: 37449 | Registered: May 1999  |  IP: Logged | Report this post to a Moderator
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
I'm Canadian from Quebec, its whatever a little above 80% is. 60% is pass.
IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
You're wrong. 80% is what the lib'ral arts students get for their piece of paper that qualifies them to ask whether you want fries with that. A good pass is somewhere in the region of 95%.
Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
quote:
Originally posted by King of Men:
You're wrong. 80% is what the lib'ral arts students get for their piece of paper that qualifies them to ask whether you want fries with that. A good pass is somewhere in the region of 95%.

Seriously dude I already got an authority figure who acts like that and who berates me for underachieving, whats your problem? At least with my professor I know he genuinely cares about me succeeding on a personal level, whats with you? Whats your excuse? Surely you remember back in Crusader Kings helping me with linked lists, I understood it in the end after the roughly 4 hours of what was probably frustrating for both of us, but hey I got it in the end.
IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
I remember that, yes. I also remember thinking you were being kind of slow. I understand it better now. Brains atrophy when not used, like any other muscle.

I am disgusted by ignorance wherever I find it, whether or not I care about its possessor's fate. Seriously. There is absolutely no excuse for this. It's as bad as creationism, without even the thin excuse of brainwashing; you're just lazy. You're letting the side down. The one advantage rational people have in presenting truth, and geeks have in getting the girls, is that we are more intelligent than the competition. And you can't multiply single-digit numbers! There are chimpanzees that can memorise this kind of thing. The likes of Ron and Lisa can do it.

Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
I think your misunderstanding, I can multiply X and Y, I just can't do it for some numbers without having to do it by writing it down and "carrying the one". And yes I can do single digit numbers your misunderstand.
IP: Logged | Report this post to a Moderator
rivka
Member
Member # 4859

 - posted      Profile for rivka   Email rivka         Edit/Delete Post 
KoM, that was rude and inappropriate. No personal attacks.

[Razz]

Posts: 32919 | Registered: Mar 2003  |  IP: Logged | Report this post to a Moderator
Belle
Member
Member # 2314

 - posted      Profile for Belle   Email Belle         Edit/Delete Post 
You know what's really sad? I have an English degree and I can do more math in my head than Blayne.

In all seriousness, you do need to think long and hard about what you're planning to do if these mathematical concepts don't come easily to you. It's not so much that you haven't memorized tables (which every 3rd grader should know) but a lack of ability to apply any mathematical knowledge that you are exhibiting here.

Unless, of course you're just yanking everyone's chain and being obnoxious.

Posts: 14428 | Registered: Aug 2001  |  IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
quote:
Originally posted by Blayne Bradley:
I think your misunderstanding, I can multiply X and Y, I just can't do it for some numbers without having to do it by writing it down and "carrying the one". And yes I can do single digit numbers your misunderstand.

Mmph. That's something, then. There's still the issue of not knowing how to calculate an expectation value. Really, now.
Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
Rappin' Ronnie Reagan
Member
Member # 5626

 - posted      Profile for Rappin' Ronnie Reagan   Email Rappin' Ronnie Reagan         Edit/Delete Post 
If people would stop answering Blayne's questions whenever he posts this kind of thread maybe he'd stop asking and figure the answers out himself.
Posts: 1658 | Registered: Sep 2003  |  IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
That's what I said, but fugu wouldn't listen to me.
Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
fugu13
Member
Member # 2859

 - posted      Profile for fugu13   Email fugu13         Edit/Delete Post 
I was typing well before you said it, but true, I would have disregarded anyways. He's not going to look it up even if not told, and I pointed out a few different ways of doing things (so hopefully he'll remember one of them in the future).
Posts: 15770 | Registered: Dec 2001  |  IP: Logged | Report this post to a Moderator
BlackBlade
Member
Member # 8376

 - posted      Profile for BlackBlade   Email BlackBlade         Edit/Delete Post 
quote:
Originally posted by Rappin' Ronnie Reagan:
If people would stop answering Blayne's questions whenever he posts this kind of thread maybe he'd stop asking and figure the answers out himself.

It does not take much effort typically to help Blayne out in these sorts of things. It's getting him to accept one legitimate criticism of Chinese or Russian government that is of epic difficulty.
Posts: 14316 | Registered: Jul 2005  |  IP: Logged | Report this post to a Moderator
MrSquicky
Member
Member # 1802

 - posted      Profile for MrSquicky   Email MrSquicky         Edit/Delete Post 
Blayne's problem is not really that he doesn't know basic things. That's more of a symptom of his basic problem, which is that he is unwilling to do things, every very easy things, for himself.

When you give him the answers to things like this, you are hurting, not helping him.

Right now, he's a terrible programmer, ignorant of both basic coding and debugging techniques and fundamentals on which elegant, efficient code rests. He can't figure out the answers to extremely simple programming problems using a google search. And he's this way in part because there are people on Hatrack who don't seem to care about him that are willing to answer his questions for him. But at the level he's at now, especially with his attitude and lack of a decent self-improvement skill set, he's never going to be able to get or at least hold a decent programming job.

And, Jebus help me, I actually think he might be smart enough to do so. He just needs to grow up an awful lot.

Posts: 10177 | Registered: Apr 2001  |  IP: Logged | Report this post to a Moderator
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
quote:
Originally posted by fugu13:
I was typing well before you said it, but true, I would have disregarded anyways. He's not going to look it up even if not told, and I pointed out a few different ways of doing things (so hopefully he'll remember one of them in the future).

I considered averages as "add up all the numbers and divide by the total" which incidentally is 3.5, I just didn't really believe it. So I came for confirmation..... I just realized ust this second is essnetially what 1/6 + 2/6 + 3/6 + ... + 6/6 is. *facepalm*
IP: Logged | Report this post to a Moderator
Blayne Bradley
unregistered


 - posted            Edit/Delete Post 
Now to figure out an easy way to add up all of the positive integers of n for larger numbers like a d100 as adding up 100 + 99 + 98... will probably take a while.

Whats the version of Factorial called where they're adding it up to find the sum and not finding the product?

just the name, I dont need a demonstration.

IP: Logged | Report this post to a Moderator
Strider
Member
Member # 1807

 - posted      Profile for Strider   Email Strider         Edit/Delete Post 
quote:
You're wrong. 80% is what the lib'ral arts students get for their piece of paper that qualifies them to ask whether you want fries with that. A good pass is somewhere in the region of 95%.
actually, i think it's the other way around.

I was always really frustrated with my liberal arts friends who were earning As really easily, in classes I could've earned those kinds of grades in as well. Meanwhile I was struggling in extremely hard science and programming classes, earning lower grades and doing much more work.

Posts: 8741 | Registered: Apr 2001  |  IP: Logged | Report this post to a Moderator
King of Men
Member
Member # 6684

 - posted      Profile for King of Men   Email King of Men         Edit/Delete Post 
I'm aware that they get easy As in their own courses. I meant that in the one math course they're required to take, they get 80%.

Blayne, that's a classic case of why you should pay attention in class. That problem is famous.

Posts: 10645 | Registered: Jul 2004  |  IP: Logged | Report this post to a Moderator
Strider
Member
Member # 1807

 - posted      Profile for Strider   Email Strider         Edit/Delete Post 
true. and even that one math course was so simplified for their major. And here I was banging my head against the wall in differential equations and linear algebra.
Posts: 8741 | Registered: Apr 2001  |  IP: Logged | Report this post to a Moderator
Sean Monahan
Member
Member # 9334

 - posted      Profile for Sean Monahan   Email Sean Monahan         Edit/Delete Post 
quote:
Originally posted by Blayne Bradley:
Now to figure out an easy way to add up all of the positive integers of n for larger numbers like a d100 as adding up 100 + 99 + 98... will probably take a while.

Whats the version of Factorial called where they're adding it up to find the sum and not finding the product?

just the name, I dont need a demonstration.

Here's a hint: Carl Gauss came up with a formula for this when he was in grade school, though the story may be apocryphal.
Posts: 1080 | Registered: Apr 2006  |  IP: Logged | Report this post to a Moderator
  This topic comprises 3 pages: 1  2  3   

   Close Topic   Feature Topic   Move Topic   Delete Topic next oldest topic   next newest topic
 - Printer-friendly view of this topic
Hop To:


Contact Us | Hatrack River Home Page

Copyright © 2008 Hatrack River Enterprises Inc. All rights reserved.
Reproduction in whole or in part without permission is prohibited.


Powered by Infopop Corporation
UBB.classic™ 6.7.2