
Nuggetpouch
Registered: 08/08/04
Posts: 2,035
Last seen: 4 years, 7 months

elementary statistitcs question. plz HELP!
#11272186  10/18/09 06:11 PM (8 years, 1 month ago) 


i have a midterm tomorrow and i'm looking at one of the questions on the study guide, the answer is not provided so there's no way of knowing if i did the question right. can anyone answer it for me so we can compare our answers?
The question is: 50 marbles are in a jar; 5 white; 4 pink; 41 gray. If 2 marbles are drawn out at random, without replacement, what is the probability of getting one white marble and one pink marble?
Plzzzz save my ass
 My statistical assumption is that chemical tapering should begin when the rate of visiting ODD exceeds the rate of visiting Pub, or any other Shroomery forum.

learningtofly
Ancient Aliens
Registered: 05/21/07
Posts: 15,105
Loc: Out of this world
Last seen: 6 years, 4 months

Re: elementary statistitcs question. plz HELP! [Re: Nuggetpouch]
#11272206  10/18/09 06:15 PM (8 years, 1 month ago) 


4/490


Jair
Smeghead
Registered: 06/08/07
Posts: 2,593
Loc: East Coast
Last seen: 5 months, 16 days

Re: elementary statistitcs question. plz HELP! [Re: Nuggetpouch]
#11272210  10/18/09 06:16 PM (8 years, 1 month ago) 


Let's see.
You are looking for a white and a pink marble. So S=[PW] + [WP]. These are the only combinations you can have of white and pink marbles with only two draws. But WP and PW are different, so be sure to include both.
P(P)= 4/50 P(W)= 5/50
S=[4/50 x 5/50] + [5/50 x 4/50]
The answer is .016 or 1.6%

Edited by Jair (10/18/09 06:17 PM)

Nuggetpouch
Registered: 08/08/04
Posts: 2,035
Last seen: 4 years, 7 months

Re: elementary statistitcs question. plz HELP! [Re: learningtofly]
#11272212  10/18/09 06:16 PM (8 years, 1 month ago) 


hmm i got 20/2450, which i guess is an unsimplified version of your answer.... can we verify that this is correct?
EDIT: yeah i dont think this is right....
 My statistical assumption is that chemical tapering should begin when the rate of visiting ODD exceeds the rate of visiting Pub, or any other Shroomery forum.
Edited by Nuggetpouch (10/18/09 06:18 PM)

learningtofly
Ancient Aliens
Registered: 05/21/07
Posts: 15,105
Loc: Out of this world
Last seen: 6 years, 4 months

Re: elementary statistitcs question. plz HELP! [Re: Jair]
#11272219  10/18/09 06:18 PM (8 years, 1 month ago) 


Quote:
Jair said: Let's see.
You are looking for a white and a pink marble. So S=[PW] + [WP]. These are the only combinations you can have of white and pink marbles with only two draws. But WP and PW are different, so be sure to include both.
P(P)= 4/50 P(W)= 5/50
S=[4/50 x 5/50] + [5/50 x 4/50]
The answer is .016 or 1.6%
did you account for w/out replacement????????????!?!??!??!


Jair
Smeghead
Registered: 06/08/07
Posts: 2,593
Loc: East Coast
Last seen: 5 months, 16 days

Re: elementary statistitcs question. plz HELP! [Re: learningtofly]
#11272224  10/18/09 06:19 PM (8 years, 1 month ago) 


Quote:
learningtofly said:
Quote:
Jair said: Let's see.
You are looking for a white and a pink marble. So S=[PW] + [WP]. These are the only combinations you can have of white and pink marbles with only two draws. But WP and PW are different, so be sure to include both.
P(P)= 4/50 P(W)= 5/50
S=[4/50 x 5/50] + [5/50 x 4/50]
The answer is .016 or 1.6%
did you account for w/out replacement????????????!?!??!??!
DOH, I thought it said with replacement, sorry OP I'm stoned.

Edited by Jair (10/18/09 06:19 PM)

Nuggetpouch
Registered: 08/08/04
Posts: 2,035
Last seen: 4 years, 7 months

Re: elementary statistitcs question. plz HELP! [Re: Jair]
#11272225  10/18/09 06:19 PM (8 years, 1 month ago) 


Quote:
Jair said: Let's see.
You are looking for a white and a pink marble. So S=[PW] + [WP]. These are the only combinations you can have of white and pink marbles with only two draws. But WP and PW are different, so be sure to include both.
P(P)= 4/50 P(W)= 5/50
S=[4/50 x 5/50] + [5/50 x 4/50]
The answer is .016 or 1.6%
You forget that there is no replacement, you really did help clear things up for me with the sample space but it would actually be [4/50 x 5/49] + [5/50 x 4/49]
 My statistical assumption is that chemical tapering should begin when the rate of visiting ODD exceeds the rate of visiting Pub, or any other Shroomery forum.

Jair
Smeghead
Registered: 06/08/07
Posts: 2,593
Loc: East Coast
Last seen: 5 months, 16 days

Re: elementary statistitcs question. plz HELP! [Re: Nuggetpouch]
#11272233  10/18/09 06:20 PM (8 years, 1 month ago) 


Quote:
Nuggetpouch said:
Quote:
Jair said: Let's see.
You are looking for a white and a pink marble. So S=[PW] + [WP]. These are the only combinations you can have of white and pink marbles with only two draws. But WP and PW are different, so be sure to include both.
P(P)= 4/50 P(W)= 5/50
S=[4/50 x 5/50] + [5/50 x 4/50]
The answer is .016 or 1.6%
You forget that there is no replacement, you really did help clear things up for me with the sample space but it would actually be [4/50 x 5/49] + [5/50 x 4/49]
Yeah, I thought it said with replacement, sorry!


Jair
Smeghead
Registered: 06/08/07
Posts: 2,593
Loc: East Coast
Last seen: 5 months, 16 days

Re: elementary statistitcs question. plz HELP! [Re: Jair]
#11272256  10/18/09 06:23 PM (8 years, 1 month ago) 


I still got the same answer.


Nuggetpouch
Registered: 08/08/04
Posts: 2,035
Last seen: 4 years, 7 months

Re: elementary statistitcs question. plz HELP! [Re: Jair]
#11272259  10/18/09 06:23 PM (8 years, 1 month ago) 


Quote:
Jair said: Let's see.
You are looking for a white and a pink marble. So S=[PW] + [WP]. These are the only combinations you can have of white and pink marbles with only two draws. But WP and PW are different, so be sure to include both.
P(P)= 4/50 P(W)= 5/50
S=[4/50 x 5/50] + [5/50 x 4/50]
The answer is .016 or 1.6%
oh and what does S stand for again?
thx for all your helps by the way
 My statistical assumption is that chemical tapering should begin when the rate of visiting ODD exceeds the rate of visiting Pub, or any other Shroomery forum.

Jair
Smeghead
Registered: 06/08/07
Posts: 2,593
Loc: East Coast
Last seen: 5 months, 16 days

Re: elementary statistitcs question. plz HELP! [Re: Nuggetpouch]
#11272263  10/18/09 06:25 PM (8 years, 1 month ago) 


Quote:
Nuggetpouch said:
Quote:
Jair said: Let's see.
You are looking for a white and a pink marble. So S=[PW] + [WP]. These are the only combinations you can have of white and pink marbles with only two draws. But WP and PW are different, so be sure to include both.
P(P)= 4/50 P(W)= 5/50
S=[4/50 x 5/50] + [5/50 x 4/50]
The answer is .016 or 1.6%
oh and what does S stand for again?
thx for all your helps by the way
My professor is Asian and I can't really understand her so I just copy what she has on the board, and she uses "S." I'm pretty sure it means sample or sample space though.


Nuggetpouch
Registered: 08/08/04
Posts: 2,035
Last seen: 4 years, 7 months

Re: elementary statistitcs question. plz HELP! [Re: Jair]
#11272274  10/18/09 06:26 PM (8 years, 1 month ago) 


Quote:
Jair said: I still got the same answer.
yeah your right... the answer is still 1.6% even if you do it without replacement... thats weird.... i guess that 1 extra marble not being accounted for is just too insignificant to change the answer anything worth not rounding
 My statistical assumption is that chemical tapering should begin when the rate of visiting ODD exceeds the rate of visiting Pub, or any other Shroomery forum.
Edited by Nuggetpouch (10/18/09 06:29 PM)

Nuggetpouch
Registered: 08/08/04
Posts: 2,035
Last seen: 4 years, 7 months

Re: elementary statistitcs question. plz HELP! [Re: learningtofly]
#11272283  10/18/09 06:28 PM (8 years, 1 month ago) 


Quote:
learningtofly said: 4/490
and is this even corerct? i think the correct answer simplified is actually 4/245... you forgot to account for the fact that there are TWO possible ways to get a white and a pink. you can get a white on the first and a pink on the second OR a pink on the first and a white on the second... am i right on this?
i think im finally starting to get it
 My statistical assumption is that chemical tapering should begin when the rate of visiting ODD exceeds the rate of visiting Pub, or any other Shroomery forum.

Jair
Smeghead
Registered: 06/08/07
Posts: 2,593
Loc: East Coast
Last seen: 5 months, 16 days

Re: elementary statistitcs question. plz HELP! [Re: Nuggetpouch]
#11272297  10/18/09 06:31 PM (8 years, 1 month ago) 


Quote:
Nuggetpouch said:
Quote:
learningtofly said: 4/490
and is this even corerct? i think the correct answer simplified is actually 4/245... you forgot to account for the fact that there are TWO possible ways to get a white and a pink. you can get a white on the first and a pink on the second OR a pink on the first and a white on the second... am i right on this?
i think im finally starting to get it
4/245 is correct, and you are right on the different combinations. I don't ever think about the big picture though you could make a tree diagram and see what you need, just too much work.


Nuggetpouch
Registered: 08/08/04
Posts: 2,035
Last seen: 4 years, 7 months

Re: elementary statistitcs question. plz HELP! [Re: Nuggetpouch]
#11272302  10/18/09 06:33 PM (8 years, 1 month ago) 


also i need help with 1 more question.
50 marbles are in a jar; 5 are white, 25 are black, 10 are blue, 6 are orange, and 4 are pink. If 2 marbles are drawn out and random, without replacement, what is
a) the probability of getting at most one white marble?
b) the probability of getting no white marbles if the first marble drawn is orange?
 My statistical assumption is that chemical tapering should begin when the rate of visiting ODD exceeds the rate of visiting Pub, or any other Shroomery forum.

Neuron
Tek Savant
Registered: 12/28/08
Posts: 5,778
Loc: @meriKa
Last seen: 7 years, 2 months

Re: elementary statistitcs question. plz HELP! [Re: Nuggetpouch]
#11272365  10/18/09 06:46 PM (8 years, 1 month ago) 


The math textbook you have should have examples of each kind of problem...


Jair
Smeghead
Registered: 06/08/07
Posts: 2,593
Loc: East Coast
Last seen: 5 months, 16 days

Re: elementary statistitcs question. plz HELP! [Re: Nuggetpouch]
#11272373  10/18/09 06:47 PM (8 years, 1 month ago) 


Quote:
Nuggetpouch said: also i need help with 1 more question.
50 marbles are in a jar; 5 are white, 25 are black, 10 are blue, 6 are orange, and 4 are pink. If 2 marbles are drawn out and random, without replacement, what is
a) the probability of getting at most one white marble?
b) the probability of getting no white marbles if the first marble drawn is orange?
Ahh, this is more fun!
a) "At most one white marble" includes 1 white marble and no white marbles. That is a lot of combinations to think of so use this trick: 1(Ac). For this complementary thing, you are finding what it ISN'T asking for and subtract from one. Your sample space has to be S=[WW]. Any other combination includes 1 or 0 whites so we can't use those.
P(W)= 5/50
S=1  [5/50 x 5/49]
Answer: .01 or 1%
b) Ok so Orange is always first in your samples for this question and you can't have any whites. S=[OBla] + [OBlu] + [OO] + [OP]
P(O}= 6/50 P(Bla)= 25/50 P(Blu)= 10/50 P(P)= 4/50
S=[6/50 x 25/49] + [6/50 x 25/49] + [6/50 x 6/49] + [6/50 x 4/49]
Answer: Don't want to do this on my computer calculator.
THIS MIGHT NOT ALL BE CORRECT, I AM REALLY HIGH!

Edited by Jair (10/18/09 07:01 PM)

learningtofly
Ancient Aliens
Registered: 05/21/07
Posts: 15,105
Loc: Out of this world
Last seen: 6 years, 4 months

Re: elementary statistitcs question. plz HELP! [Re: Jair]
#11272474  10/18/09 07:10 PM (8 years, 1 month ago) 


Quote:
Jair said:
Quote:
Nuggetpouch said:
Quote:
Jair said: Let's see.
You are looking for a white and a pink marble. So S=[PW] + [WP]. These are the only combinations you can have of white and pink marbles with only two draws. But WP and PW are different, so be sure to include both.
P(P)= 4/50 P(W)= 5/50
S=[4/50 x 5/50] + [5/50 x 4/50]
The answer is .016 or 1.6%
oh and what does S stand for again?
thx for all your helps by the way
My professor is Asian and I can't really understand her so I just copy what she has on the board, and she uses "S." I'm pretty sure it means sample or sample space though.
generally N is population and n is sample.


Nuggetpouch
Registered: 08/08/04
Posts: 2,035
Last seen: 4 years, 7 months

Re: elementary statistitcs question. plz HELP! [Re: learningtofly]
#11272502  10/18/09 07:15 PM (8 years, 1 month ago) 


Okay, I have one last question and I just wanted to see if my answers were correct.
25 planes approaching earth, each plane is programmed to randomly select one of two airports and land at it, the airports are aplha and beta.
A) What is the probability that all 25 planes land at site aplha?
B) What is the probability that at least 1 plane lands at site alpha?
 My statistical assumption is that chemical tapering should begin when the rate of visiting ODD exceeds the rate of visiting Pub, or any other Shroomery forum.

Jair
Smeghead
Registered: 06/08/07
Posts: 2,593
Loc: East Coast
Last seen: 5 months, 16 days

Re: elementary statistitcs question. plz HELP! [Re: Nuggetpouch]
#11272584  10/18/09 07:28 PM (8 years, 1 month ago) 


Quote:
Nuggetpouch said: Okay, I have one last question and I just wanted to see if my answers were correct.
25 planes approaching earth, each plane is programmed to randomly select one of two airports and land at it, the airports are aplha and beta.
A) What is the probability that all 25 planes land at site aplha?
B) What is the probability that at least 1 plane lands at site alpha?
A) 1/2 to the power of 25 because S=[AAAAAAAAAAAAAAAAAAAAAAAAA]
and P(A)= 1/2
B) Do the opposite trick again. 1(Ac). "At least one plane at alpha" includes everything but 0 alphas. This is S=[B to the power of 25]. Since both A^25 and B^25 are P= 1/2, you can just subtract your answer from question A from one.
1B^25.
Edit: Make sure you finish out the problem, I just didn't have my calc around.

Edited by Jair (10/18/09 07:29 PM)

