[QUOTE=download;48878060]I'm aware. I thought I made that clear.
I was asking that if the presenter's choice is random then there's no advantage to switching.[/QUOTE]
The presenters choice isn't random.
The presenter knows what is where, and only by this knowledge does the whole paradox work.
Hmm
[QUOTE=Bradyns;48878070]The presenters choice isn't random.
The presenter knows what is where, and only by this knowledge does the whole paradox work.[/QUOTE]
I thought so.
I heard about the problem many years ago but thought it was ridiculous. Only the other day when I found out that the presenter always chooses goats did it seem true.
[editline]11th October 2015[/editline]
I have to wonder how many people would think the question was less ridiculous if they knew that. It doesn't seem to be common knowledge.
[QUOTE=download;48877170]Anyone interested in discussing the Monty Hall problem?
I've been doing some reading on it recently and I think I found the trip up on it.
The problem is that you randomly pick a door, and then the presenter opens the door you haven't picked [I]that contains a goat[/I] (or one of them if you've picked the car). People make the mistake in thinking the presenter randomly chooses a door.
I can't prove it mathematically (though I could probably make a model that proves it experimentally in Excel) but I suspect that if the presenter chooses the goat door then it's statistically a better option to switch while if the presenter just randomly chooses a door there is no statistical advantage to switching.[/QUOTE]
This is exactly how I'd explain it to a layman. Let me do the calcs to prove that if he chooses randomly, you get no benefit.
Yep, if we consider the policies "always switch" and "switch with prob 1/2" they get the same victory probabilities if Monty is drunk and picks any door (other than the one you have chosen) randomly. If he picks the car door you instantly lose, for obvious reasons.
I can post the working if you are interested, but its mostly brute forcing the 3 decisions (your initial door, Monty's door, your decision to stick or switch).
[QUOTE=Wunce;48878311]This is exactly how I'd explain it to a layman. Let me do the calcs to prove that if he chooses randomly, you get no benefit.
Yep, if we consider the policies "always switch" and "switch with prob 1/2" they get the same victory probabilities if Monty is drunk and picks any door (other than the one you have chosen) randomly. If he picks the car door you instantly lose, for obvious reasons.
I can post the working if you are interested, but its mostly brute forcing the 3 decisions (your initial door, Monty's door, your decision to stick or switch).[/QUOTE]
Eh, if it bugs me enough I'll model it.
I have to say though, few explanation for the problem I've seen say that the presenter chooses a goat every time. I'm convinced that trips pretty much everyone up.
[QUOTE=download;48878400]Eh, if it bugs me enough I'll model it.
I have to say though, few explanation for the problem I've seen say that the presenter chooses a goat every time. I'm convinced that trips pretty much everyone up.[/QUOTE]
Weird. Every single time I've heard it explained it's been stated rather clearly that the presenter makes sure to only expose goats (and yet even then a lot of people apparently can't grasp it).
[QUOTE=sltungle;48878564]Weird. Every single time I've heard it explained it's been stated rather clearly that the presenter makes sure to only expose goats (and yet even then a lot of people apparently can't grasp it).[/QUOTE]
Of course, if the presenter exposes a goat, the show is over. I guess you could assign a 0% probability to winning after switching if you do that, but what would be the point?
i need to take a matrix algebra class to get a math minor with my elec eng degree. is it hard? i looked up the prof on ratemyprofessor and he doesn't seem too bad
class descrip:
[quote]Textbook: Linear algebra and its applications (4th edition) by David C. Lay, ISBN 0-321-38517-9.
Matrix algebra has its roots in the study of simultaneous linear equations in several variables. The development of systematic methods to find and to discuss the solutions of linear equations has lead to fundamental concepts and methods such as matrix, Gaussian elimination, vector space, dimension, linear transformation, determinant, eigenvalue, inner product. The goal of the course is to become very familiar with all these objects.
Ideas, methods, and the language of matrix algebra are widely used in all areas of mathematics and most other sciences. The course will basically cover Chapters 1-7 of the textbook.
[/quote]
No, matrices and linear algebra are pretty easy, both computationally and theoretically.
Doing shit with matrices by hand can get tedious but it's never actually hard. Tons of upper-level math basically involves structures that allow us to reduce certain problems to linear algebra because it's so simple.
alright cool. i'll try to fit it in my schedule somewhere
I'd say it depends on your background, in retrospect after seeing vector spaces and inner products and tensors and whatnot, it is indeed not that hard, but when I saw that shit for the first time I had no idea what I was doing. Did pass it on the first sitting, as opposed to calculus :v:
i'm taking calc 3 rn and i think i'm doing alright. got an 80 on the last exam about vectors and 3d space and shit. doing partial derivatives and gradients and they're ez
[QUOTE=elitehakor;48879537]i'm taking calc 3 rn and i think i'm doing alright. got an 80 on the last exam about vectors and 3d space and shit. doing partial derivatives and gradients and they're ez[/QUOTE]
you'll be fine then. Computation in vector calc is harder than in linear algebra.
I find linear algebra so dull, though. At least until you do multilinear algebra or talk about vector bundles and what not instead of just regular old vector spaces
-snip-
[QUOTE=JohnnyMo1;48879708]you'll be fine then. Computation in vector calc is harder than in linear algebra.
I find linear algebra so dull, though. At least until you do multilinear algebra or talk about vector bundles and what not instead of just regular old vector spaces[/QUOTE]
Multilinear algebra really does look interesting, just looked at it.
I just wanted to vent out that reading about maths and seeing my Econ degree study topics, I feel like I'm being trained to be a cheap optimization problem resolver. Like, focusing only on the math part that deal with that kind of problem.
I don't whether to drop Economics or follow mathematics. I love dealing with "what's the best path for this truck to follow" or "How do you assing these resources in order to...." or solving Cobb Douglas equations and finding optimums and maximums.
I wonder if I would be better at those things studying Economics or just Applied Mathematics.
But there's a cost. I'm 3 years away from getting my degree at the UTDT (Best uni in econ of Argentina) or starting Lic.in Mathematics (Can be later on applied or abstract) at the UBA, which would take around 6 years....
OR maybe a Master/PhD in mathematics? Would that be feasible or useful for an economist?
[QUOTE=Cutthecrap;48887314]I just wanted to vent out that reading about maths and seeing my Econ degree study topics, I feel like I'm being trained to be a cheap optimization problem resolver. Like, focusing only on the math part that deal with that kind of problem.
I don't whether to drop Economics or follow mathematics. I love dealing with "what's the best path for this truck to follow" or "How do you assing these resources in order to...." or solving Cobb Douglas equations and finding optimums and maximums.
I wonder if I would be better at those things studying Economics or just Applied Mathematics.
But there's a cost. I'm 3 years away from getting my degree at the UTDT (Best uni in econ of Argentina) or starting Lic.in Mathematics (Can be later on applied or abstract) at the UBA, which would take around 6 years....
OR maybe a Master/PhD in mathematics? Would that be feasible or useful for an economist?[/QUOTE]
It sounds like you are interested in general optimization and decision making. I suggest you take a look at some Operations Research - it has applications to finance but goes far broader. In fact I recommend everyone try Ops Research at least once. I was initially turned off by the name, but it is actually really fun.
I can't really comment on your study situation though, you should probably talk to an academic adviser about it.
I might quit Math college, not because I don't like Math but because currently stuff and professors are so boring. I am gonna continue to learn about Math myself @ home. We have internet and books, don't we?
[QUOTE=Fourier;49022180]I might quit Math college, not because I don't like Math but because currently stuff and professors are so boring. I am gonna continue to learn about Math myself @ home. We have internet and books, don't we?[/QUOTE]
Do you plan on pursuing some other degree?
Anyone care to find any mistakes in my solution of an ODE? When I enter it in Matlab it seems to blow up because a is positive and b negative, resulting in an exponential with a positive argument (and a numerical solution does not blow up for the same parameters).
[URL="https://drive.google.com/file/d/0B9gPhhwaE3ZReVRWcTFDZl9CN2c/view?usp=sharing"]Link[/URL]
This is like the first time in 4 years of college physics that I actually needed this method :v:
[QUOTE=Number-41;49026766]Anyone care to find any mistakes in my solution of an ODE? When I enter it in Matlab it seems to blow up because a is positive and b negative, resulting in an exponential with a positive argument (and a numerical solution does not blow up for the same parameters).
[URL="https://drive.google.com/file/d/0B9gPhhwaE3ZReVRWcTFDZl9CN2c/view?usp=sharing"]Link[/URL]
This is like the first time in 4 years of college physics that I actually needed this method :v:[/QUOTE]
Integration by parts with sinusoidal functions can suck a dick...
I can't see anything immediately erroneous though, so it's probably something miniscule.
Matlab is renowned for its unforgiving nature; have you got the the exact code you input into Matlab handy?
I just put it into the report that I might have made a mistake (deadline was tonight) :v: They actually didn't ask for the exact solution but the numerical solution is pretty boring and it's difficult to write a 3 page report on it.
This might be a stupid question, but I haven't done calculator-less math properly in quite some while and I'm wondering if there are any fast methods to do questions like these without having to do long division on paper (for a multiple choice test):
"A company gives a 12% discount to his customers on retail price. If
the total is over $10,000 after the discount, they give an additional 3%
discount on the remaining balance. A customer’s total came to $13,500
(discounted price). How much did he save?"
"John purchased a jacket at a 7% discount. He had a membership
which gave him an additional 2% discount on the discounted price. If he
paid $425, then what was the retail price of the jacket?"
I presume the first thing to do would be to look and see how far apart the answers are so that I can break it down into manageable chunks for speed, but is there any way to negate the long division so that I don't have to do stuff like this for the answer which would take quite some time on paper with long divison?:
"Let the original price be x, then at the rate of 7% the discounted price
will be = 0.93x. 2% discounted amount then will be = 0.02 × 0.93x =
0.0186x. The remaining price=0.93x-0.0186x=0.9114x. This is the
amount which John has paid so 0.9114x = 425. X = 425/0.9114. Solving
for X = 466.31"
Thank you mathematicians!
[QUOTE=Falubii;49022274]Do you plan on pursuing some other degree?[/QUOTE]
I will continue this one, but I won't go to courses. I will learn this stuff myself. Will see how it goes, I really only have 1.5 years left to finish this.
And yes, I wish to study other stuff, like bioinformatics, robotics. Will see how it goes :v:.
[QUOTE=Tophat;49028970]This might be a stupid question, but I haven't done calculator-less math properly in quite some while and I'm wondering if there are any fast methods to do questions like these without having to do long division on paper (for a multiple choice test):
"A company gives a 12% discount to his customers on retail price. If
the total is over $10,000 after the discount, they give an additional 3%
discount on the remaining balance. A customer’s total came to $13,500
(discounted price). How much did he save?"
Thank you mathematicians![/QUOTE]
First write down all the facts.
12%,
10000$
13500$
Then just think a bit..
Discounted money:
13500 - 10000 = 3500
Word equation:
12% Discount on X$ = 3500$
Equation:
X - 0.12X = 3500$
0.88X = 3500$
Final result:
X = 3500 * (1/0.88)
Something like that I think :)
Shit, I never knew until today that a countable union of countable sets being countable relies on the axiom of (countable) choice.
[QUOTE=JohnnyMo1;49085850]Shit, I never knew until today that a countable union of countable sets being countable relies on the axiom of (countable) choice.[/QUOTE]
that sounds completely made up, so it must be true
Is non-quantifiable data useful in a k-nearest neighbor algorithm?
for example, if one dimension was music preference, could I simply give an id number to each genre of music (rock: 1, Rap: 2, etc.) and get the k-nearest neighbor with those as an axis, or since they have no quantifiable relationship with one-another, are they useless as metrics?
[QUOTE=proboardslol;49168990]Is non-quantifiable data useful in a k-nearest neighbor algorithm?
for example, if one dimension was music preference, could I simply give an id number to each genre of music (rock: 1, Rap: 2, etc.) and get the k-nearest neighbor with those as an axis, or since they have no quantifiable relationship with one-another, are they useless as metrics?[/QUOTE]
Unless you can come up with a sensible measure of distance between genres, it doesn't sound like a very good idea.
One thing you could do instead is create a binary attribute for each genre and set it to 1 if person likes it and 0 otherwise.
[QUOTE=Falubii;49022274]Do you plan on pursuing some other degree?[/QUOTE]
I am continuing studying now, somehow I am working and studying at same time :v:
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