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The Urn - May 12, 2010
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Spiked Math Comic - The Urn

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Professor, what is a box?

It's kind of like an urn.

p(white, white) = 4/7 * 3/6 = 0.285714286

yes, I was bored :)

mathematicians also suck a spelling I mean seriously look at y=mx+b
how does m stand for slope?

A student asked me a couple years back. Since I didn't want to get sidetracked, I suggested that it had something to do with Greek, Latin or maybe French. I then offered extra credit to anyone who could find out why it was m (with some proof).

End result: the research said no one was sure. One of those notations that's lost with time.

In sweden, we write it as y=kx+m, and m stands for the swedish word for coefficient (which is spelled with a k). It is still not clear what the m stands for however.

Sigh. And how does "y" stand for "value"? There are so many letters needed in mathematics that mathematicians need other alphabets.

Also, who said everything needs to be in English? If, say, half of our math was developed by Hindu peeps, why would they care about your weird words?

Dude, chill!
I was intrigued by the "also suck at".
Also, the letter is never relevant, the definition is. It's the same case with the box and the urn. Those are subterfuges for easier understanding.

Google it! Result: http://www.math.duke.edu/education/webfeats/Slope/Slopederiv.html, which says that nobody really knows. "It just happened."

By the way, what's a Grecian urn?

Oh, about ten Drachmas a day.

*badumpbumb ching*

I just had that from two international students. I had to admit that I hadn't used the term myself since the last cremation. That didn't help the discussion much.

A student with poor mathematical analysis skills, no doubt. Solving the problem is not dependent on whether you know what an urn is.

I always thought "m" came from the French word for mountain, "montagne." And I thought Decartes used it first.

According to the web page above, he didn't.

box, what is a professor?


Why do all students look so dis-interested, bored, sleepy? C'mon ppl this is a maths class and that too probabilities..yay!!!

I think it should be 4C2/7C2. 4/7 * 3/6 means u r removing the balls one after the other which is not the current scenario. Here both the balls are being removed together. Though the answer would be the same in both cases.Please enlighten if I am wrong...

The answer is the same, because the end result is the same. The caveat "without replacement" means that the time between when you choose them is immaterial. It could be 3 milliseconds or 3 hours, it's still removing two and not putting the first one back.

Student: What's an urn?
Teacher: It is like a vase that you can stick your hand in the top of to collect the marbles but it is difficult to see into so that you do not inadvertently take a peek at the colors. If we use a box instead and you lean over to collect the marbles you will probably influence which colors you pick even if you mean to to it at random.

A fitting illustration on my Masters Thesis re disadvantage to ESL students caused by language of mathematics

Of course, for "selection without replacement day", one could bring in an actual urn and teach several things at once... "This is an urn. This is a vase. This urn has four white and three red marbles. You can see them. ... [much later] ... So, class, what were the odds that this student would get a bit of glass embedded in his arm when we shattered the urn and from that estimate the odds that it will happen again *to the same student* when we smash the vase."

Student: "Um, zero, since he left..."


If a box contains four white marbles and three red ones, what is the probability that one of the marbles gets eaten by Schrodinger's cat?

So how much does a professor urn?

Not enough.

Urn! Urn!! Urn!!!..... Yawn Urn!!!

m stands for 'motha freaking slope'

I was about to ask how old the kids were, but then I realized any kid old enough to be doing probability should know what an urn is...

happened to me exactly the same.

Coefficients for the slope and intercept are sometimes written as letters of the Greek alphabet; Mu and Beta, which turns into "m" and "b" in an English font. No source, just an educated guess.

A container holds 4 units of A and 3 units of B; if 2 units are selected at sufficient entropy from the container in this universe, what is the probability that the result is 2 units of A?

What is unity?

I agree--change it to box. I mean, I know what an urn is, but I didn't realize this problem format, i.e. referencing marbles-in-an-urn, was so common. I thought it was just *my* stats book that was goofy like that.

Of course what would actually be even better would be to *change* the units/container terminology frequently to various bland things, and occasionally something non-bland to wake the students up.

Furry cows moo and decompress.

I TA'd for an intro stats course and there problem was to find the probability that a four sided die would roll a 2. A student was convinced there was no such thing as a 4 sided die... so I pulled out my D&D dice and showed him my D4 (yes I carry my dice on me at all times. You never know when you have a MTG game come up or a campaign). Eventually the professor gave up and made all the problems with dice be D6s.

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