Romes
Joined: Jul 22, 2014
• Posts: 5556
March 12th, 2015 at 6:50:46 AM permalink
Quote: sodawater

Well, this is infuriating.

My friend is enrolled in an introduction to statistics class at a community college, and she just sent me this question from her quiz:

(Click image for bigger version)

Her answer of "false" has been graded as incorrect. I assured her that the probability was 0.15 and therefore "false" was correct, so she e-mailed the professor.

The professor replied that "true" was indeed correct "because of the multiplication rule, 8/20 times 3/20." Despite her objections, he is leaving the answer as incorrect.

This is why you don't ever want to go to community college.

I wish we could actually set up the described bag and gamble on it if he really thinks the probability is 0.06 instead of 0.15.

Why are you multiplying by 8/20?
- For the red marbles
But isn't the 3/20 accounting for 3 of those 8 red marbles already?
- I, ugh... multiplication rule!

lol
Playing it correctly means you've already won.
RS
Joined: Feb 11, 2014
• Posts: 8623
March 12th, 2015 at 6:54:32 AM permalink
My brother who is pretty good at writing, somehow ended up in the "I have no clue wtf grammar, spelling, how to read or write, etc." course at his college -- it's like English 001 or something. He sent me a picture (this was a while ago, don't have it anymore) of the teacher's response on the top of the paper. It read something like:

"Good storyline, neads improvment, not long enouf in lenth", and with awful hand-writing to go along with it. I wish I still had the picture, it was hilarious.

I guess there were numerous times in the class when the professor was just flat out wrong (not taking into account his horrible spelling). For example, he'd end sentences with propositions, would use "he" instead of "him" or "me" instead of "I", and its/it's was wrong a lot, too.

I had a professor who had us do an assignment (computer science, a programming project) where you actually could not do what he wanted. I submitted my version of the project, with the note saying something like: "This project is not possible using his language." If I remember correctly, he wanted us to do something like the following (in Java or C++?):

Quote:

1. int main() {
2. int a = 5;
3. cout << a << "\n";
4. modify(a);
5. cout << "A has changed: " << a << "\n";
6. }
7.
8. int modify(int x) {
9. x = x*5;
10. return x;
11. }

And that was actually what he wanted us to do! His response to my project was "see attached code" and was the code I wrote above (well, in the context, slightly different, but that's not the point).

The point is, in C++ or Java or w/e language it was -- when you pass integers to a function [ie: line #4], you are only transfering the VALUE of the variable a, not the actual address of a. So, in the modify function, on line 9, it creates a new variable with a new address that has the value (of 5). And when that value is returned, it does not actually change the value of the variable a, since the address to a is never used when modifying it.

No, we were not supposed to use pointers. I even asked him beforehand, and he said not to use pointers because we had not gone over pointers yet. And no, we weren't supposed to do something like:

Quote:

a = modify(a);

I emailed him, saying the problem was unfair, since it's not possible to do that. I showed him the code he provided didn't actually do what the assignment had asked us to do, screenshot included. We went back and forth, and he firmly stood his ground for several emails. But eventually he gave in, and gave me 100% on the project.

I had another professor who had us do a....I'm not sure exactly what it's called, but basically we had to do an experiment, make a power point, then do a screen-conference thing and present it to her, individually. So basically, everyone would do theirs on their own specific time. I don't remember when it was, but, basically my time was schedule for, let's say, June 9'th at 10am. I cancelled the plans I had for that day [since I was previously planning on going out of town for a few days before and a few days after, no Internet service where I was going, and no way I could'a done the presentation had I not been at home]. Well, long story short, I check my email on like June 3'rd or 4'th, and surprise surprise! An email saying I had gotten a 0% for not presenting my thing on June 2'nd at 10am. It was one of those automated emails.

I emailed the professor, saying my thing was schedule for June 9'th. She said no, it was June 2'nd. I looked back through previous emails with her, which confirm June 2'nd. I looked through the syllabus, and there weren't even any time slots open for June 2'nd. We went back and forth, and I go nowhere. I asked to "reschedule" to June 9'th, and she said no. I asked if I could do it today or tomorrow, and she said no. What had happened is, she was using a syllabus and dates from the previous year, and the dates don't always match up from year to year. A lot of students were doing group-projects and I was doing mine solo. I guess the group-presentation time/date slots were changed properly and the solo time/date slots weren't changed. So everyone in groups got the correct time slot, while those who were by themselves got the wrong time slot. But there were only 1 or 2 other people doing it solo, and I suppose they talked with students in the group-projects and figured out the dates were off by 7 days.

ANYWAY, I brought it up with my counselor [who is pretty much an airhead], but he couldn't do anything about it. I took it up with the administration department (or w/e department is in charge of this kinda stuff) and it's been a total mess.

The worst part of it is, the presentation was worth like 40% of my grade, which means there's no way to pass the class getting a 0% on it. On top of that, the class is only offered every-so-often, so I have to wait until it's offered again to take it. And that class is a pre-requisite for other classes, meaning I can't take those other classes before I pass the one I had just failed. And each of those are pre-requisites for the next classes to be taken.

So now I'm stuck dealing with the administration department / my counselor or whoever is in charge of this stuff, trying to either re-take the class or get it changed to an A so I can continue taking classes I should be taking.
zoobrew
Joined: Jan 12, 2015
• Posts: 309
March 12th, 2015 at 7:15:25 AM permalink
Quote: AZDuffman

Meh. Don't try to confuse this kind of professor with logic. That a person could get to a Masters Degree and miss something so simple is just amazing.

I would give a pass if it was a case of, "crap, I worded that wrong." Looking at the prof's logic and I cannot even tell what they are trying to figure out.

First you are fooling yourself if you think that it requires a masters degree to teach at a community college or that they are a Professor. Second having read other posters on this board, many of whom would be qualified to teach at community colleges, reject gambling logic why are you surprised? Lastly the vast majority of community college teachers are just fine, especially when you are only paying \$80 a credit.

You could have as your teacher a grad student who is a PhD candidate by day at Carnegie Mellon University and by night the alleged leader of meth ring.
AxelWolf
Joined: Oct 10, 2012
• Posts: 20283
March 12th, 2015 at 7:45:57 AM permalink
To much school talk going on here, it's bringing back bad memories of that horrible 6am alarm clock. I'm going back to bed.
♪♪Now you swear and kick and beg us That you're not a gamblin' man Then you find you're back in Vegas With a handle in your hand♪♪ Your black cards can make you money So you hide them when you're able In the land of casinos and money You must put them on the table♪♪ You go back Jack do it again roulette wheels turinin' 'round and 'round♪♪ You go back Jack do it again♪♪
Romes
Joined: Jul 22, 2014
• Posts: 5556
March 12th, 2015 at 7:50:29 AM permalink
Quote: RS

I had a professor who had us do an assignment (computer science, a programming project) where you actually could not do what he wanted. I submitted my version of the project, with the note saying something like: "This project is not possible using his language." If I remember correctly, he wanted us to do something like the following (in Java or C++?):

(CODE)

And that was actually what he wanted us to do! His response to my project was "see attached code" and was the code I wrote above (well, in the context, slightly different, but that's not the point).

The point is, in C++ or Java or w/e language it was -- when you pass integers to a function [ie: line #4], you are only transfering the VALUE of the variable a, not the actual address of a. So, in the modify function, on line 9, it creates a new variable with a new address that has the value (of 5). And when that value is returned, it does not actually change the value of the variable a, since the address to a is never used when modifying it.

int modify(int &x) {
...
}
Pass by reference? Or was he saying to do that w/out passing by reference? Then yeah, you'd have to set a variable to the int result getting passed back.

I've got one of the best "professor" experiences (that probably gave me one of my 2 ulcers)... I tested in to calculus, but wanted to take trig as a refresher/GPA booster my freshman year 1st quarter. So I signed up, took this class, went every day, did the homework, then came the exams. I took the first exam thinking "yeah I got a 100% on that.." Well, when the exams came back I saw "50/100 UNCLEAR"... I looked at each of the problems and none of them were marked 'wrong' per say. There were no 'corrections' just a single line through each problem that said "UNCLEAR" next to it.

Since when is it possible/allowable to say 2+2=4 is wrong because you don't like the way it's written??? I showed my work on every problem. Next exam, same result. ALL right answers, showing my work, but all slashes with "UNCLEAR" resulting in a 50/100. I spoke with the professor after the first exam and he stated that I had to show my work differently. I politely explained that I will try to show it however he wanted, but at the end of the day my answers were all right and he couldn't mark them wrong. So after the 2nd exam I was going to drop the class. I met with the professor to ask him again why I got a 50/100 with all the correct answers, showing my work, and doing the problems per his instruction. He said he'd just give me a C in the class if I got at least a C on the final. Being a dumb, young freshman I agreed, but here comes the best part: I cheated on the final and still got 50/100. Two things: 1) He encouraged us to have sheets of paper for doing/showing our work that we would later turn in with our exams. 2) He always left the room for at least 20-30 minutes at a time, just stopping in to 'check' on us every now and then (in hindsight wow he didn't even stay in the room to answer questions, what a dick). Anyways, I put 1 & 2 together... I got 3 pages of scrap paper, and then I also pulled my notes from class out (detailing how "he liked" every problem solved). I copied line for line how he solved the problems in class, arriving at all correct answers once again for what should have been my 3rd 100% exam. When the grades came out, I saw that he failed me. He suckered me in to taking the final so he could fail me.

I took my case to the dean of the math department, whom told me the professor has tenure and reserves the right to grade how he chooses. I couldn't believe it. 2+2 does NOT equal 4 apparently. I threatened to go to the local news stations with my exams, showing all the right answers and how I showed my work to get to those answers. Again, in hindsight, I really should have followed through on that. He was an awful professor. I ended up taking Trig and Calc next quarter at the same time (much against my advisers recommendations) and got an A in both (shockingly). The only thing I learned from him was ratemyprofessors.org. I never took another shitty professor and thankfully he was one of the very few at my university. Before anyone asks, no it wasn't community, and it was a fairly prestigious university. This guy was both an outlier and a douche. I still remember his ridiculously thick german accent. His english was UNCLEAR.
Playing it correctly means you've already won.
FleaStiff
Joined: Oct 19, 2009
• Posts: 14484
March 12th, 2015 at 7:55:40 AM permalink
Quote: sodawater

The professor replied that "true" was indeed correct "because of the multiplication rule, 8/20 times 3/20." Despite her objections, he is leaving the answer as incorrect.

Took me a while.
ThatDonGuy
Joined: Jun 22, 2011
• Posts: 5452
March 12th, 2015 at 11:50:51 AM permalink
The word the professor should be looking for is "independent." The multiplication rule applies only when all of the variables are independent. In this case, the probability of a red marble having a sticker <> the probability of a non-red marble having a sticker, so whether or not a marble has a sticker is not independent of the marble's color.

In fact, the multiplication rule can apply, but it should be 8/20 (the probability that a marble is red) x 3/8 (the probability that a red marble has a sticker).

Hopefully, the professor won't go on to prove that 7 x 13 = 28. (See Lou Costello for details on this one.)
Wizard
Joined: Oct 14, 2009
• Posts: 24506
March 12th, 2015 at 12:00:01 PM permalink
Quote: sodawater

I wonder if the Wizard can chime in and shame this professor.

Three of the marbles in a bag of 20 are red and have a sticker. So obviously the probability is 3/20 = 15%. The professor is over-thinking it.

My advice to the student is to appeal it to the chairman of the math department.
It's not whether you win or lose; it's whether or not you had a good bet.
Kerkebet
Joined: Oct 2, 2014
• Posts: 362
March 12th, 2015 at 12:25:14 PM permalink
Quote: Wizard

So obviously the probability is 3/20 = 15%.

Wouldn't the serious or seasoned gambler readily approximately account, or at least allow, for the possibility that the stickers may transfer between marbles as randomized in a bag?
Nonsense is a very hard thing to keep up. Just ask the Wizard and company.
Romes
Joined: Jul 22, 2014