Our new Indie Games subforum is now open for business in G&T. Go and check it out, you might land a code for a free game. If you're developing an indie game and want to post about it, follow these directions. If you don't, he'll break your legs! Hahaha! Seriously though.
Our rules have been updated and given their own forum. Go and look at them! They are nice, and there may be new ones that you didn't know about! Hooray for rules! Hooray for The System! Hooray for Conforming!
Stats Question
Fuzzy Cumulonimbus Cloud
Registered User regular
Registered User regular
I am in now way trying to get someone to do my homework. If there are four management posisitions, and there are 5 womeon and 7 men, what is the chance that the trainee class is all men? We're supposed to do a (n,C,r) for probability, but shouldn't the probability be 20%, because we know the outcomes can only be 0 women, 4 men; 1 woman, 3 men; et cetera, giving us 5 possible outcomes. I have the combination answer, but I still don't know why I would need to do the combination in the first place.
Fuzzy Cumulonimbus Cloud on
Posts
man1, man2, man3, man4
man1, man2, man3, man5
...
man4, man5, man6, man7
etc.
There are only 5 possible outcome bins with respect to the number of men and women, but there are many possible combinations and they don't result in an even split between bins, so the probability is not just 1/5.
If you do what Daenris did and list out every single possible combination, then count the portion that are entirely men, you won't get 20%:
m1m2m3m4
m1m2m3m5
...
w1w2m1m2
w1w2m1m3
...
etc.
Second example: There is going to by 7C2*5C2 different ways it could be two of each. This is because their are 7C2 ways of picking two out of 7 and 5C2 ways of picking 2 from 5.
Where you say there are 5 possible outcomes. That is true, but each of these outcomes have different probabilities. In the same way that rolling a 7 on two dice isn't 1/11 even though there are 11 different outcomes.
The simplest way to refute your statement is that there are only 11 possible outcomes when you roll and sum up 2 six-sided dice (the standard 2d6 roll in most RPGs), but that doesn't mean you have a 1/11 chance to get a 2 or 12. You actually have a 1/36 chance to get a 2, and a 1/6 chance to get a 7. In other words, the outcomes are not equivalent to the probability. This is a common misconception that leads to things like The Birthday Paradox and the like.
Yes, stats is weird. Also, don't trust an answer just because it "sounds" right. That's part of the fun of stats. I use the term "fun" loosely.
Also, I get either 7.0% or 7.3%, depending which way I go. I think it's 7.0%.
It's a stats problem, so I doubt it's a trick question. It sounds like a basic combination problem.
7C4 is the number of combinations that can be made with your 7 men, and there are 12C4 possible groups.
7*6*5*4 / 4 * 3 * 2 * 1 = 35
12 * 11 * 10 * 9 / 4 * 3 * 2 * 1 = 495
35 / 495
But yeah.
This. Statistics isn't really interested in asking you a question and then saying 'ololz, all menz r janitors'*. Now, you could very well be asked to describe flaws in an approach, as understanding the limitations and assumptions of a methodology is important, but it should be obvious when that happens.
Equal probability of each item is actually a normal assumption in statistics. If it doesn't hold, you'll probably be told.
* Or, in fact, the reverse of this, which is a real concern in some fields. But menz is a fun word.
Take the advice of someone who's taken several classes in statistics. When it comes to calculating probabilities, throw your "common sense" out the window. It never works. Do the process.
probability = (# of ways something happens)/(# of ways anything happens)
= (# of ways to choose 4 men from 7)/(# of ways to chose any 4 from total)
= (7C4)/(12C4) = .... = 7/99
aka what musanman wrote.
NEVER EVER EVER
Seriously, the words "common sense" and "sounds about right" are your worst fucking enemies in a basic stats class, because the entire point of the class is often to throw problems at you were the answer is either not intuitive or actively counter-intuitive, thus forcing you to learn the process.
Sadly. D:D:D:D:D:
For paintings in progress, check out canvas and paints
"The power of the weirdness compels me."