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# Forum: Probability

Probability course and homework discussion. Probability distributions. Probability theory, stochastic processes

1. ### Sticky: We only provide homework help to those who show effort

Welcome to Talk Stats Forum. In order to keep homework help effective and efficient, we request all members to abide by these guidelines: 1)...

• Replies: 0
• Views: 30,307
09-30-2005, 09:44 AM
1. ### 15 people (including you) apply for 7 jobs. What are your chances of getting the job?

Hi :wave: Allow me to extend my thanks to you all for taking the time to visit this thread. I came across this seemingly simple probability...

• Replies: 16
• Views: 7,238
12-30-2011, 02:39 PM
2. ### Moment Generating Function

If the joint moment generating function of X and Y is M X,Y (t1, t2) = 6 / (1-t1) * and X,Y are the times that required for two tasks to be...

• Replies: 16
• Views: 5,734
02-23-2012, 01:13 PM
3. ### Difficulty setting up double integrals for Joint Distributions

I'm struggling to set up the correct range when calculating probabilities of joint distributions....anyone have any recommended reading or sites that...

• Replies: 16
• Views: 9,016
09-30-2012, 03:24 AM
4. ### Will two Independent Variables transformed into two functions remain independent?

X & Y are independent variables. X ~ Bernoulli(1/2), Y ~ Bernoulli(1/3). Let Z = X + Y and W = X - Y. Compute Cov(Z,W) and Corr(Z,W). Am I...

• Replies: 16
• Views: 3,049
10-07-2012, 11:36 PM
5. ### counting rule?

20 students have to be split into 5 different labs groups; how many ways can we partition them if the first 3 labs have 3 students, the 4th has 5...

• Replies: 15
• Views: 6,171
09-20-2010, 10:52 AM
6. ### problem on gamma distribution

let X_1,X_2,......,X_n be 'n' i.i.d random variables, each following gamma (1,3) distribution. show that P(X_1+X_2+.....X_n > 3(n-\sqrt{n}) ) >...

• Replies: 15
• Views: 7,793
11-01-2010, 07:15 AM
7. ### Normal distribution problems

I'm having some issues with a few questions on my practice final. Let X be a normally distributed random variable with expectation = -1 and...

• Replies: 15
• Views: 5,638
12-20-2010, 02:38 PM
8. ### Proof of covariance of a weak stationary stoch. process.

Hey there. I'm having trouble on how to show this is true. Assuming you have a weakly stationary independent increments stochastic process with ...

• Replies: 15
• Views: 6,797
c2q
02-05-2012, 04:22 PM
9. ### Can't seem to solve this p(x+y>1)

Given f(x,y) = 3x/2 for 0<x<1 , -x<y<x Find P(x+y>1) .

• Replies: 15
• Views: 5,476
04-01-2012, 07:13 PM
10. ### [SOLVED] Probability problem help(how to do)

A gardener has a bag with 12 wildflower seeds saved from wildflowers in summer. She plants 4 of them at random in a pot to see if they will grow...

• Replies: 15
• Views: 3,264
09-22-2012, 08:21 PM
11. ### Need help on problem BIG TIME!

Each trading day the value of a particular stock goes up one unit with probability 0.3, stays the same with probability 0.5 or else goes down one...

• Replies: 14
• Views: 3,556
03-18-2008, 11:16 PM
12. ### Hopefully an easy 'first post'!

Hi All. I'm a newbie to the forums, and will hopefully introduce myself with an eay-enough question on probability! OK, here goes: I have...

• Replies: 14
• Views: 5,130
09-09-2008, 03:01 PM
13. ### Help with A HOMEWORK PROBLEM

Hello to all Daryl shuffles a standard deck of cards (13 cards in each of four suits) and draws one card. Then Daryl replaces the card, shuffles...

• Replies: 14
• Views: 4,417
01-12-2009, 10:36 AM
14. ### X=0 almost surely => E(X)=0

Axioms of expectation: 1. X>0 => E(X)>0 2. E(1)=1 3. E(aX+bY) = aE(X) + bE(Y) 4. If X_n is a nondecreasing sequence of numbers and lim(X_n) = X,...

• Replies: 14
• Views: 4,541
07-20-2009, 12:59 AM
15. ### E[MSE] simple linear regression

Hi All- I am trying to figure out how to prove that MSE = SSE/n-2 is an unbiased estimator of sigma^2 in simple linear regression. I have that...

• Replies: 14
• Views: 41,659
02-02-2013, 03:44 AM
16. ### need help with proof issues

1) given: (1+x)^n =SUM nCk X^k, prove that SUM nCk p^k q^n-k =1,where p+q=1 2)prove the general law of addition:P(E1 U E2 U......U En)=SUM...

• Replies: 14
• Views: 4,873
09-14-2010, 04:04 PM

Hey all, I'm currently a stats student and i have run into confusion about some questions pertaining to probability. I have attempted the following...

• Replies: 14
• Views: 4,684
01-20-2011, 12:06 PM
18. ### Probability question

I read the sticky in this section about trying the problem before posting the question but I don't know where to begin on this problem. Any help...

• Replies: 14
• Views: 11,656
04-03-2011, 04:15 PM
19. ### r-value > Probability

I have two wrestlers who are going to arm-wrestle. I want to try to predict who will win based on their previous fights against other opponents....

• Replies: 14
• Views: 7,047
08-24-2011, 06:14 AM
20. ### need help to calculate variance of sales

Hi, I'm trying to calculate numerical value of the variance of sales, and the probability of a sale greater than 6300 cans. but it seems wrong...

• Replies: 14
• Views: 6,781
09-21-2011, 07:18 PM
21. ### Three shooters, probability that two of them hits

I have a little problem. There are three shooters ( i= 1,2,3) and they hit the target with probabilities P(A1) = 1/2, P(B1) = 2/3, P(A3) = 3/4....

• Replies: 14
• Views: 5,238
10-24-2011, 01:18 AM
22. ### probability of winning with every failed attempt

Hello, I am trying to figure out what the probability of "losing" on a task is after every failed attempt, where each time there is no evidence of...

• Replies: 14
• Views: 2,863
BGM
11-01-2011, 01:36 PM
23. ### Binomial

machine has 3 wheels each with 40different numbers, the problem need to find the probabilty of have 3 apples in the case where 1) 3 times in...

• Replies: 14
• Views: 2,815
12-07-2011, 07:02 AM
24. ### Random Variable X

So this question is on my practice final, and the professor provided the work for how to solve it and I cannot figure it out. Suppose that the...

• Replies: 14
• Views: 6,553
12-13-2011, 09:03 PM
25. ### Bayesian updating over multiple distributions

Say I believe a basketball player's likelihood distribution of making a shot is affected by his distance from the hoop, how well he is being...

• Replies: 14
• Views: 3,214
01-22-2012, 04:00 PM
26. ### Question about mutually exclusive probability

How do i find mutually exclusive probability? it says in my book that if p(A or B) = p(a) + p(b) then the events are mutualy exclusive. Or does it...

• Replies: 14
• Views: 6,795
10-06-2012, 08:19 PM
27. ### Independent die roll

Hi i have this problem, where a fair die is rolled until the same number occurs 2 successive times. Let X be the trial on which the repeat occurs,...

• Replies: 14
• Views: 2,227
11-22-2013, 08:59 AM
28. ### Bayesian and Probability

A certain disease has infected 2% of the population. The firm has annoucned that 90% of those infected will show a postive test result , while 95% of...

• Replies: 14
• Views: 2,562
03-18-2015, 03:39 PM
29. ### Urgent: Probability of having Lyme Disease and Bayes theorem

I recently found a deer tick on me (had been there for several days). I have no symptoms. My Dr. says I could ignore it or take a course of...

• Replies: 14
• Views: 1,852
03-13-2017, 06:02 PM
30. ### Probability

Ok I am very new to stats and am very confused. I went to the examples board and now am even more confused. Here is the problem. Ok they offer a...

• Replies: 13
• Views: 5,894
11-15-2005, 03:11 PM
31. ### Determining Joint PDFs, and Marginal PDFs

Hi All, I'm going through revision questions, and I am stuck on this particular section all with similar questions. If somebody can give me a guide...

• Replies: 13
• Views: 12,886
05-15-2008, 01:04 AM
32. ### stupid question sample variance

Hi there, I have a rather stupid question suppose I have the values of the random variable X: for example. (That's right the third...

• Replies: 13
• Views: 5,359
12-15-2008, 11:44 AM
33. ### Method of Moments, MLEs, and Standard Errors

Hi, I have a question about standard errors in the context of this problem. Any help would be greatly appreciated: Suppose X is a discrete random...

• Replies: 13
• Views: 14,019
BGM
02-07-2010, 04:13 PM

The random variable x represents the number of boys in a family of three children. Assuming that boys and girls are equally likely, find the mean and...

• Replies: 13
• Views: 6,320
10-27-2010, 09:12 PM
35. ### How to get this number?

a) Variant P(x=0)=P(0,0)+P(0,1)+P(0,2)=0.27 P(x=1)=P(1,0)+P(1,1)+P(1,2)=0,4 P(x=2)=P(2,0)+P(2,1)+P(2,2)=0.33 expected value ( I do not know how...

• Replies: 13
• Views: 3,589
11-24-2010, 12:16 PM
36. ### Cumulative Beta Distribution Function Help

Hi everyone, I was wondering if someone could help me figure out how this function works. My problem is not that I need homework help, it's that...

• Replies: 13
• Views: 12,633
05-05-2014, 04:07 AM
37. ### conditional binomial is a poisson distribution

Hi, I'm fighting with this problem for a while. There is something important I'm missing So the problem goes like this X~Poisson(lambda) and Y|X=k...

• Replies: 13
• Views: 22,197
10-21-2015, 04:01 PM
38. ### A question about sampling

Consider two probability distributions, A and B. A has greater variance than B, but A and B have equal means. We are not told anything about their...

• Replies: 13
• Views: 3,740
04-27-2012, 09:52 AM
39. ### Monte carlo conditioning

I am trying to learn how to reduce variance with conditioning. page 15 in these lecture notes: http://www.columbia.edu/~mh2078/MCS_Var_Red1.pdf ...

• Replies: 13
• Views: 3,044
alf
11-26-2011, 10:43 AM
40. ### *Rate of Ruin & Optimal N

For a fair coin toss game, both prob(ruin) & prob(consecutive losses) increases with no. of trials. Is the Rate of ruin .i.e.where prob(ruin)...

• Replies: 13
• Views: 3,881
11-28-2011, 12:21 PM

An insurance company's records suggest that experienced drivers (those aged over 21) submit claims at a rate of 0.1 per year, and inexperienced...

• Replies: 13
• Views: 2,900
01-17-2012, 10:31 PM
42. ### Tricky question on probability?!

A fair dice with 6 sides is rolled a certain number of times and the numer 1-6 is recorded each time it is rolled. Which of the following sequences...

• Replies: 13
• Views: 3,221
nyo
10-10-2012, 08:35 PM
43. ### Two Random Variables Normal Distribution

X1 ~ N(3,2^2), X2 ~ N(-8, 5^2) Let U = X1 - 5X2 Let V = -6X1 + CX2, where C is constant. (a) What are the distributions of U and V? I know U ~...

• Replies: 13
• Views: 4,615
10-19-2012, 11:00 PM
44. ### Odds of a certain 5 character string occurring in a random string of 512.

I work in security and recently had a false positive happen where a certain word that was being tested occurred in the session id. Matching is not...

• Replies: 13
• Views: 2,982
11-16-2012, 09:51 PM
45. ### Simple Bernoulli question

I am sort of baffled by this. The point is to simulate how often students will be right when guessing on a multiple choice tests with 5 responses. It...

• Replies: 13
• Views: 3,447
10-13-2014, 03:24 PM
46. ### Estimating a distribution

Hi, Suppose I had some bags containing a large number of black and white marbles. Each bag has a uniform distribution, but I don't know in advance...

• Replies: 12
• Views: 5,015
08-08-2011, 02:36 AM
47. ### Probabilty of picking higher number

I am working on a webbased game, and need help with some probability. Player A rolls a 20 sided die with the numbers 1 through 20. Player B rolls...

• Replies: 12
• Views: 3,545
08-28-2008, 12:02 AM
48. ### Binomial Formula ?

Hi everyone, I'm absolutely going crazy trying to figure this problem out, and I know the answer LOL..I just can't figure out how they got it. Using...

• Replies: 12
• Views: 3,578
10-19-2008, 10:25 PM
49. ### Help! First time taking Stats and soooo confused!

I'm taking Statistics online and every week I can barely get through the assigned problems. I'm not sure how to even begin figuring out this...

• Replies: 12
• Views: 5,447
11-06-2008, 09:53 AM
50. ### I still need help please

Ok, so I am still working on this freaking problem. Can someone help me please. It states that the scenario is normally distributed with a mean price...

• Replies: 12
• Views: 22,995
12-14-2009, 09:10 PM
51. ### Probability of an Event

There is probably a very simple answer to this, but please help a stats novice. I am trying to determine the probability of an event occurring in...

• Replies: 12
• Views: 9,307
02-03-2010, 09:00 PM
52. ### Expected Value Problem

The heights of all male students in a university have mean 170 centimetres and standard deviation 10 centimetres. Three male students are randomly...

• Replies: 12
• Views: 6,911
10-17-2010, 10:23 PM
53. ### Probability of 2 Heads Question

I came across an interesting and counter-intuitive problem in my statistics course recently and wanted to share it with you guys to see if you could...

• Replies: 12
• Views: 3,019
10-26-2010, 03:14 PM
54. ### Correlation of the product of 2 multivariate normal variables...

hello everyone! i've got a quick theoretical question that i'm gearing towards a simulation exercise but i need to get my stuff right first... ...

• Replies: 12
• Views: 5,966
07-28-2011, 01:33 AM

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