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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: 30,199
09-30-2005, 09:44 AM
1. States of a Transition probability matrix

Hi there, I have a question about the states on a Markov chain that I was hoping some one might be able to explain to me. Say for instance...

• Replies: 0
• Views: 3,252
02-06-2012, 11:48 AM
2. Help

An interview has been done among a group of students. It is found that 10% have hot breakfast, 20% have hot lunch and 25% have a hot breakfast or a...

• Replies: 2
• Views: 1,490
02-06-2012, 07:46 AM
3. Proving some axioms about sigma algebra.

I have the following to prove: Given a sigma field/sigma algebra B on a set S. Prove: i) 0 E B ii) if B1,..,Bk E B then UBi E B for i = 1 to n...

• Replies: 9
• Views: 7,586
02-05-2012, 10:32 PM
4. Find the sample size

Given info: cost1=$4, σ1=10, W1=N1/N=0.4 cost2=$9, σ2=20, W2=N2/N=0.6 The first part of this question asks for the values of n1/n and n2/n that...

• Replies: 0
• Views: 1,392
02-05-2012, 05:08 PM
5. Poisson distribution and moment generating function question

This is a problem my professor assigned for homework. He said if we can't do it, it's not a big deal; it's a difficult problem. I'd still like to...

• Replies: 3
• Views: 5,753
02-05-2012, 04:45 PM
6. Gaussian process proof.

I want to prove that the brownian bridge is a gaussian process. Before I start I just wanted to make sure of something. In my notes my...

• Replies: 0
• Views: 2,932
c2q
02-05-2012, 04:29 PM
7. 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: 6,756
c2q
02-05-2012, 04:22 PM
8. Help with a proof

If x1...xk are random variables defined on a set omega, and B1...Bk C R^1, then prove that (x1,....,xk)^-1 (B1x,...,xBk) = x1^-1B1 n x2^-1B2 n ......

• Replies: 2
• Views: 2,307
c2q
02-04-2012, 03:41 PM
9. [SOLVED] Correlation between two normal variables ...

Suppose A ~ N (0,a), B ~ N (0,b-a), C = A + B what is the expression for the correlation between A and C?

• Replies: 17
• Views: 6,874
02-04-2012, 11:48 AM
10. quick question: probability of being dealt a royal flush?

if you have a standard deck of cards and are dealt 5 cards randomly, what are the chances of getting a royal flush? i feel like this is pretty...

• Replies: 5
• Views: 8,591
02-02-2012, 05:57 PM
11. Bayes Estimator for Bernoulli/Beta

Let X be number of successes out of n items The prior is a beta distribution. n := 20 a := 5 b := 10 I need to determine the number of...

• Replies: 1
• Views: 2,983
BGM
02-02-2012, 12:51 PM
12. [SOLVED] New to Probability

Hello! I am taking my first stats course in University, and I am normally pretty good with number (finished with A+s in linear algebra, and...

• Replies: 5
• Views: 4,260
02-01-2012, 11:17 PM
13. negative predictive value/ probability

\begin{tabular}{|r|rr|} \hline &postive results & negative results\\ \hline pregnant & 80 & 5\\ not pregnant &...

• Replies: 2
• Views: 2,517
02-01-2012, 03:06 PM
14. Marginal Densities of 3 Joint Normal r.v.s in Polar Coordinates

Hey all, So fun question. X, Y and Z are independent ~ N(0,sigma^2). x = r*sin(phi)*cos(theta) y = r*sin(phi)*sin(theta) z = r*cos(phi) 0 <=...

• Replies: 6
• Views: 3,834
02-01-2012, 11:12 AM
15. Actuarial Exam P

Sorry if this isn't really the best place for this question. I passed the exam P and am just trying to figure out how I can determine how many...

• Replies: 0
• Views: 3,563
01-31-2012, 01:22 PM
16. difference between binomial exact test and fisher's exact test

Hello all, So I know the general difference between these tests --binomial exact test is used to test for a significant difference between and...

• Replies: 1
• Views: 18,332
01-31-2012, 11:04 AM
17. Student, Density, Donald Duck

Hi to all! I don`t know to do this tasks, so I would much apriciate if someone can help :confused: 1) Student needs to answer on n independent...

• Replies: 2
• Views: 2,846
01-31-2012, 07:05 AM
18. Gamma-Poisson - Hierarchical Model

I have two variables, T = time of person to do a certain task and N = number of steps that person takes to do this task. T has as gamma distribution...

• Replies: 3
• Views: 3,843
01-30-2012, 10:54 PM

The Isserlis theorem states that if is a zero mean multivariate normal random vector, then : E = EE + EE + EE Now, in the case x,y,z,t are...

• Replies: 0
• Views: 63,202
01-30-2012, 12:38 PM
20. Easy question check

Say event B . = to Event C .the probability of their intersection would be 1? I think this is not true because, there could be other outcomes...

• Replies: 1
• Views: 1,836
BGM
01-30-2012, 12:19 PM
21. Simple probability question

I've been writing up some basic code for my own trading to show things like, if I have a 70% chance of losing, and each time I lose 5%, I would...

• Replies: 9
• Views: 2,395
BGM
01-30-2012, 05:00 AM
22. Cycle of permutation Problem

Dear everyone, I have questions about cycle of permutation. Here are the questions. For ones who haven't heard about cycle, Anyway, I...

• Replies: 3
• Views: 4,802
01-30-2012, 01:04 AM
23. [SOLVED] Sensitivity/Specificity

Here is my question: The sensitivity of a screening test is 0.95 and it's specificity is 0.85. The rate of the disease for which the test is used...

• Replies: 24
• Views: 7,512
01-29-2012, 11:08 PM
24. Mean and var of maximum of n RVs from uniform dist.

I am doing a problem that focuses on the maximum of n iid discrete RVs (Ymax) of Y1,...,Yn, each having the same probability distribution with common...

• Replies: 2
• Views: 4,040
01-29-2012, 03:44 PM
25. Order Statistics for continuous RVs

Let Y1,...,Yn be iid RVs, each having uniform distribution on (q,q+1) where q is the unknown parameter to estimate. How can I show that Y_bar-1/2 is...

• Replies: 3
• Views: 2,650
01-29-2012, 01:25 PM
26. [SOLVED] Need help with a problem that I THINK requires Bayes Theorem....

For the combined ELISA-Western blot blood test for HIV positive status, the sensitivity is about 0.999 and the specificity os about 0.9999. Consider...

• Replies: 12
• Views: 6,922
01-28-2012, 03:33 PM
27. Independent events?

I don't know how to do this question...how to find if one event is independent of another. I answered the following question: After surveying...

• Replies: 4
• Views: 3,794
01-28-2012, 02:50 PM
28. Blood Groups - I think this is right?

46% of people have blood type O, 42% have type A, 9% have type B and 3% have AB. Among 4 potential donors, what is the probability that: A) all are...

• Replies: 4
• Views: 1,695
01-28-2012, 03:37 AM
29. Looking for confirmation that I'm correct...

just wondering if someone can double check this... 2 cards are randomly selected without replacement. What is the probability that neither are...

• Replies: 3
• Views: 2,057
01-28-2012, 02:51 AM

Hey Evry1..... I have been facing a problem in achieving the solution for the following question in quite some time. Kindly help me with the...

• Replies: 4
• Views: 2,069
01-27-2012, 11:57 PM

I have this question that I believe I have the correct answer for, however, I am unsure as to exactly what the proper formula is (and obviously...

• Replies: 6
• Views: 2,427
01-27-2012, 09:01 PM
32. Finding P(X-Y=0)

Hi, I have several distributions which I want to compare. They include the Burr distribution, Johnson SB, logistic and a few others. They are all...

• Replies: 2
• Views: 5,522
01-27-2012, 04:25 PM
33. basic concept check

1. If event A and B are independent, would the conditional probability of B given A=1? I say false because it should =p(B) not 1. 2. If event A is...

• Replies: 1
• Views: 1,569
BGM
01-27-2012, 03:19 PM
34. simple cdf and pdf problem?

Let X and Y be independent random variables, uniformly distributed in the interval . Find the cumulative distribution function and the probability...

• Replies: 1
• Views: 3,807
BGM
01-27-2012, 01:06 PM
35. variance of product

hi, i try to prove this property. Verify that: Var=Var.Var +Var.E^2+ Var.E^2 X,Y are independent variables. i tried the definition of variance...

• Replies: 1
• Views: 2,196
01-27-2012, 10:17 AM
36. Optimal Sampling Plan

. Quality Assurance Inspection Sampling: Consider the manufacturing process of commodity computer memory chips. In order to control outgoing...

• Replies: 0
• Views: 2,253
01-26-2012, 03:56 PM
37. Unbiased Estimator Question

Suppose that Y has a Poisson distribution with parameter lambda. How can I show that (-2)^lambda is an unbiased estimator of e^(-3*lambda)?

• Replies: 19
• Views: 7,538
01-26-2012, 11:32 AM
38. Poison or not Poison, that is the question.... (Shakespeare?)

Hello, We are investigating vehicle delivery data - which we know if it was pretty random, the arrival intervals of the vehicles will follow a...

• Replies: 1
• Views: 2,457
01-26-2012, 10:41 AM

A recent study of 300 patients found that of 100 alcoholic patients, 87 had elevated cholestrol levels, and of 200 nonalcoholic patients, 43 had...

• Replies: 1
• Views: 6,313
01-25-2012, 12:31 AM
40. Find estimator of minimum mean square error

The random variables Y1...Yn are NID with parameter u and (sigma)^2. S^2 = (using £ for summation) £ (Yi-Ybar)^2/(n-1) is an unbiased estimator of...

• Replies: 3
• Views: 3,644
01-24-2012, 12:49 AM
41. Simple stats question! Thanks!

Hello, this is just pure curiosity. If you were to have three 6 sided dice and shake them all at once in a cup and throw them at the same time, and...

• Replies: 1
• Views: 1,413
01-23-2012, 01:48 PM
42. Find unbiased estimator of minimum variance

Hi, I'm new to this area of statistics and I could really use some help. Suppose that random variables Y1 and Y2 are independent, both with mean u...

• Replies: 3
• Views: 6,315
01-22-2012, 10:16 PM
43. 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: 3,198
01-22-2012, 04:00 PM
44. Am I on the right track?

The researcher in Part A decides to compare the difference in the population proportions of supporters for a reduction in funding between taxpayers...

• Replies: 1
• Views: 1,519
01-21-2012, 11:56 PM
45. Probably a stupid question

how do i calculate the exact probablity that a number of taxpayers who support a reduction in funding falls between 342 and 375 people? (sample size...

• Replies: 6
• Views: 1,915
01-21-2012, 04:45 PM
46. Definition of (objective) Probability

There are two definition as far as I know (not including subjective probability), and each one has its problems: 1. If O is the set of all equally...

• Replies: 1
• Views: 2,589
01-21-2012, 09:54 AM
47. expectation problem

10 balls are inserted (uniformly) into five jars ..each insertion is independent from the others. compute E(X1*X2) where X1 and X2 describes the...

• Replies: 3
• Views: 3,528
01-21-2012, 08:58 AM
48. Probability Density Function of normal distribution

I have a question: Please give the probability density function of a normal distribution trun- cated to . Can anyone pls help me to solve this...

• Replies: 4
• Views: 3,318
01-20-2012, 10:21 PM
49. Markov Random Fields

Hi All, Can anyone kindly refer me to an easily explained tutorial on Markov Random Fields/Markov Networks? Thank you. Meeta

• Replies: 0
• Views: 1,525
01-20-2012, 01:33 PM
50. Product Normal Distribution

Hi, Summing normal distributions is nice and easy, providing another normal distribution. But multiplying gives the Product Normal Distribution....

• Replies: 6
• Views: 15,979
01-20-2012, 12:54 PM
51. Disease Probability

I'm stuck on a question. A doctor thinks, before testing, that the probability that his patient has XYZ disease is 85%. He tests 5 times and gets...

• Replies: 1
• Views: 1,854
BGM
01-20-2012, 07:16 AM
52. markov chain and stocks

THe price of a particular stock either increases 25% or decreases 20% in any given week. The probability of an increase in any week is 60%,...

• Replies: 1
• Views: 1,943
BGM
01-20-2012, 07:04 AM
53. Probability Function Problem

A customer is equally likely to select each of six product brands, labeled "brand one," and so forth. Let X equal the brand number selected. Let Y...

• Replies: 1
• Views: 1,690
BGM
01-20-2012, 06:59 AM
54. markov chain and probability

A factory produces a sequence of items that can be graded as good or defective. A good item is followed by another gd item with probability alpha amd...

• Replies: 1
• Views: 1,955
BGM
01-20-2012, 06:57 AM
55. Sum of k samples from a normal distribution

Hi, I'm not sure how to tackle the following question, i would greatly appreciate it if someone can help. Assume you have a room filled with...

• Replies: 2
• Views: 2,795
01-19-2012, 03:03 PM
56. Raffle with many entries per person, many prizes, limit one prize per person

Consider a raffle for which each person may buy any number of tickets. There are many prizes but each each person may only win one prize. What is the...

• Replies: 2
• Views: 7,475
BGM
01-19-2012, 01:55 PM
57. Probability of a string containing a specific substring

So I've been getting into concepts like the Library of Babel and infinite monkey theorem, and have been trying to work out how to calculate the...

• Replies: 1
• Views: 6,631
01-18-2012, 11:22 AM

the time it takes for me to reach the university from my home has a normal distribution with mean 45 minutes and standard deviation 15 minutes. I...

• Replies: 8
• Views: 2,562
01-18-2012, 01:30 AM

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