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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: 30,222
09-30-2005, 09:44 AM
1. ### expectation value(s) and gaussian stochastic process

Hi all. I do some calculations including noise described by a random variable \eta\left(t\right) which is gaussian distributed at all instants t ...

• Replies: 3
• Views: 3,546
11-09-2011, 07:00 AM
2. ### Confusion with distributions..

I have the following question and I have no idea how to solve it. 3) The population variance of the distribution for X is 100. Two random samples...

• Replies: 6
• Views: 3,293
BGM
11-09-2011, 02:38 AM
3. ### Sample distribution help!!!

I'm studying for my upcoming stats test and i can't seem to figure out this problem its been bugging me for over an hour now. I thought that i would...

• Replies: 1
• Views: 3,419
BGM
11-08-2011, 01:43 AM
4. ### Beating the odds

The mortality tables give person 'A' 5 more years to live. He/she dies after 7. The tables give a person more years to live the longer that...

• Replies: 0
• Views: 1,822
11-07-2011, 12:47 PM
5. ### maximum of parabola

Hi who determine maximum of parabola? thanks

• Replies: 5
• Views: 3,436
11-07-2011, 12:14 PM
6. ### maximum of function?

Hi who determine maximum of function? thanks

• Replies: 1
• Views: 2,517
11-07-2011, 11:36 AM
7. ### formula of parabola

Hi what is formula of parabola? thanks

• Replies: 1
• Views: 2,529
BGM
11-07-2011, 11:19 AM
8. ### Two quick problems:

Hey guys, having a bit of trouble and can't find anyone to double check my work: Mean failure rate of a communication is 1 error per 10 000 000...

• Replies: 12
• Views: 2,635
11-06-2011, 11:37 PM
9. ### 2 questions: Finding the optimal value of the mean of a standard normal distribution.

I have two questions involving the Standard Normal Distribution. The first one involves finding the optimal mean, the second one involves proving...

• Replies: 1
• Views: 2,827
BGM
11-06-2011, 04:02 PM
10. ### Expectation of random vectors.

Hi there. I'm trying to prove: Cov(X,Y) = E(XY') - E(X)(E(Y))' So i know the cov of 2 random vectors is written by Cov(X,Y) = E can...

• Replies: 9
• Views: 4,997
11-06-2011, 03:27 PM
11. ### Help with an expectation.

How do i determine: E(Y'Xb|X). I think this is the estimated variance covariance matrix but I'm not sure.

• Replies: 3
• Views: 2,914
BGM
11-06-2011, 03:10 PM
12. ### Distributive Law P[A u (B n C)]

I am trying to find a synonymous formula formula for: P = P Can anybody help me? I found somewhere that said it was equal to P but I...

• Replies: 4
• Views: 15,720
11-05-2011, 04:07 PM
13. ### Probability mass function for binomial random variable

I know that the Probability mass function for binomial random variable includes the "combination" formula as opposed to the "permutation formula". ...

• Replies: 1
• Views: 2,951
Ra0
11-04-2011, 12:46 PM
14. ### How do I calculate probability using excel?

I have 8 weeks worth of fantasy football scores from 12 different teams in a MS excel spreadsheet. Each team plays a different team every week. Is it...

• Replies: 3
• Views: 4,587
11-04-2011, 12:17 PM
15. ### Exponential Family

Hi! I'm trying to demonstrate that the following distribution is a member of the exponential family. Theta * x^(Theta-1) * exp (-x^Theta) ...

• Replies: 4
• Views: 4,301
11-04-2011, 08:29 AM
16. ### Gamma Distribution

This is my question Suppose that X  Ga(n, L). Show that E = (n(n + 1) . . . (n + k − 1))/(L^k) k , for k a positive integer. I know how to...

• Replies: 2
• Views: 3,381
11-04-2011, 07:29 AM
17. ### Random Variable/Expected Value Problem (Profit)

I thought I'd gotten the hang of these, but then the newer problems had different value types that needed to be used. This particular question asks:...

• Replies: 2
• Views: 5,790
BGM
11-03-2011, 11:57 PM
18. ### stochastic annual survival rate

Hi all, I want to simulate the trajectories over time of animal populations for which I know the annual survival rate, S, estimated in the field...

• Replies: 0
• Views: 1,756
11-03-2011, 09:41 PM
19. ### need help with chebyshev, please

a random variable X has pdf f(x)=(3/2)e^-|3x| -∞ < x < ∞ a. find the mean and variance of X b. use the chebyshev inequality to find a...

• Replies: 1
• Views: 1,732
BGM
11-03-2011, 10:57 AM
20. ### Discrete Random Variable Joint Distribution Problem?

Hello, I am really, really stuck on something that probably should be obnoxiously simple. So I have this problem: Suppose X and Y are...

• Replies: 3
• Views: 3,857
BGM
11-03-2011, 04:01 AM
21. ### Probability Help

Here is the problem: Let X denote the number on a chip drawn at random from an urn containing three chips, numbered 1,2, and 3. Let Y be the...

• Replies: 1
• Views: 3,001
BGM
11-03-2011, 02:04 AM
22. ### Multiple Regression Question

..........

• Replies: 1
• Views: 1,792
11-02-2011, 04:52 PM
23. ### Probability model for random variable

I'm stumped on this one! You roll a pair of fair dice. If you get a sum greater than 10 you win $50. If you get a double you win$30. If you get a...

• Replies: 1
• Views: 3,532
BGM
11-02-2011, 03:13 PM
24. ### Sandbagger

What is the probability of a golfer winning 3 out of 4 golf tournaments? 5 out of 7? 40 players in each tournament, players have USGA handicaps.

• Replies: 4
• Views: 2,192
11-01-2011, 09:45 PM
25. ### Indicated probability

What are the steps to arrive at the answer? A bag contains 6 red chips and 11 blue chips. Two chips are selected randomly without replacement from...

• Replies: 1
• Views: 2,261
11-01-2011, 05:32 PM
26. ### 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: 2,854
BGM
11-01-2011, 01:36 PM

a point is selected at random from the bounded region in the plane between the curves y=x^2 and y=2-x^2. let X be the x-coordinate, and Y be the...

• Replies: 1
• Views: 2,176
BGM
11-01-2011, 01:30 PM
28. ### Probability 101

Hi from Melbourne. I have a rudimentary probability question that you will probably find amusing but hopefully you can also help me! I am...

• Replies: 2
• Views: 2,125
tom
10-31-2011, 04:16 PM
29. ### method of moments and MLE question

Hello all, I have a question regarding a problem asking to obtain an estimator for theta using MLE and method of moments and then to compute the...

• Replies: 7
• Views: 5,624
10-29-2011, 08:48 PM
30. ### Help with Excell and 1 2 and 3 Standar Deviations

I was given the following data: 45, 89, 78, 85, 47, 25, 56, 99, 100, 98, 65, 65, 65, 56, 35, 53, 58, 57, 54, 89, 78, 75, 75, 72, 83, 84, 75, 82,...

• Replies: 1
• Views: 2,365
10-29-2011, 05:39 PM
31. ### marginal and conditional density and probability

Dear all, I really need your help in solving these questions. If X is the amount of money (in dollars) that a salesperson spends on gasoline and...

• Replies: 4
• Views: 3,846
10-29-2011, 03:23 PM

Please tell me how to solve this question correctly (Q) Buses arrive at a specified stop at 15-minutes intervals starting at 7 a.m. That is, they...

• Replies: 1
• Views: 3,475
Ra0
10-28-2011, 03:18 PM
33. ### I have a real world problem and need some guidance in solving it.

Hi, I was hoping someone more knowledgeable than myself might be able to help me out with this. I'd be happy just to be pointed in the right...

• Replies: 0
• Views: 1,738
10-28-2011, 03:08 PM
34. ### CDF of difference of two independent non-central chi square RVs each 1 d.o.f.

Hi Everyone. I'm glad to have found this forum. This is my first post. I'm interested in obtaining a simple expression (exact or approximate)...

• Replies: 0
• Views: 1,921
rhz
10-28-2011, 02:30 PM
35. ### Conditional prob question - Is my answer correct

I wondered if someone could confirm my workings... In a certain sports club, 32 % of members play football, 31 % of members play baseball, and 23...

• Replies: 0
• Views: 1,653
10-28-2011, 11:48 AM
36. ### Difficult probability question

Hi - I'm really stuck with this question. I can't find any example quite like it anywhere: Two friends, Ben and Jerry, agree to a random swap of...

• Replies: 5
• Views: 3,268
10-28-2011, 11:42 AM
37. ### hypergeometric? mean and variance

Consider a group of T persons and let a_1, \ \ldots \ , a_T denote the heights of these T persons. Suppose that n persons are selected from...

• Replies: 3
• Views: 3,438
BGM
10-28-2011, 07:42 AM
38. ### Random Variable

(Q) Suppose that it is known that the number of item produced in a factory during a week is a random variable with mean 50. i) What can be said...

• Replies: 1
• Views: 1,747
10-27-2011, 08:02 AM
39. ### conditional probability mass function

Is my solution correct (Q) Suppose that p(x, y), the joint probability mass function of X and Y, is given by p(0, 0) = 0.4 p(0, 1) = 0.2 p(1, 0)...

• Replies: 0
• Views: 2,632
10-27-2011, 04:52 AM
40. ### Expected Value Question

Plz help me with this question. I tried but couldn't get the correct answer (Q) A school class of 120 students are driven in 3 buses to a dance...

• Replies: 0
• Views: 3,612
10-27-2011, 04:48 AM
41. ### Probability question.

suppose i have a population n=90386 where: typeA=46362, typeB=22012, typeC=22012 if i choose 145 items from the population (without returning...

• Replies: 9
• Views: 2,369
10-26-2011, 09:58 PM
42. ### Can someone explain how to solve this simple problem?

Your favorite team is in the World Series. You have assigned a probability of 63% that they will win the championship. Past records indicate that...

• Replies: 5
• Views: 6,178
10-26-2011, 09:10 PM
43. ### [Question] Birthday Problem

Here is the problem, I already get the answer, \frac{r}{365 -365(\frac{364}{365})^s} What do you think?

• Replies: 1
• Views: 2,438
10-26-2011, 12:04 PM
44. ### Wheel of lucky problem

Dear everyone, Here is the problem I tried by defining the functions S(a) and C(a), where S(a) denotes the probability of player A winning if...

• Replies: 4
• Views: 2,233
10-26-2011, 11:23 AM
45. ### Sampling and Estimation (From STPM)

A random sample X1,X2,X3,...,Xn is taken from a normal population with mean "u" and variance 1. Determine the smallest sample size which is required...

• Replies: 4
• Views: 3,523
BGM
10-25-2011, 11:49 PM
46. ### Confused with the Sampling Distribution of p

Hello all, I really hope that I can get an answer. I've worked the problem out, but I keep going back and forth in my head about the answers....

• Replies: 1
• Views: 2,028
BGM
10-25-2011, 11:29 PM
47. ### Help with greater than and less than problems

I am looking for help that basically lets me know if I am on the right track with my methods of solving these problems. I have to use Excel. Please...

• Replies: 2
• Views: 2,664
10-25-2011, 02:57 PM

need help understanding this question please? the number of lightning strikes on a square kilometer of open ground in a year has mean 6 and standard...

• Replies: 1
• Views: 4,394
10-25-2011, 02:35 AM
49. ### [Question] "Supermatch" cards problem

Dear everyone, I have a question that i couldn't figure out clearly. Here is it. Here will i write down what i have been done, and please...

• Replies: 1
• Views: 2,318
BGM
10-25-2011, 02:07 AM
50. ### Hypergeometric Random Variable help!

Here's the question, I've tried all the formulas given to me in the chapter, and none are working. I'm guessing to use the mean and...

• Replies: 4
• Views: 5,855
10-24-2011, 03:01 PM
51. ### 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: 5,217
10-24-2011, 01:18 AM
52. ### Factorials

How would I solve this problem? If I roll a fair die 4 times. X is the number of times 1 or 2 are observed in 4 rolls. What is the minimum number...

• Replies: 6
• Views: 2,012
10-23-2011, 08:33 PM
53. ### Independent Event if A is a subset of B ???

I have a questions regarding Conditional Probability. Two events A and B are independent if: P(AnB)=P(A)*P(B) Is this always the case or are...

• Replies: 5
• Views: 15,766
10-23-2011, 04:55 PM
54. ### Binominal vs Geometric.....confused!!!!

Hi there, I am currently working on these questions but I don't really get how to work them out. Is it wrong to use the binomial distribution for a)...

• Replies: 0
• Views: 3,804
10-23-2011, 01:13 PM
55. ### At least n of

Consider a genetic mutation. For anyone that has this mutation, there is a 50% probability their child(ren) will also have it. If the child has the...

• Replies: 3
• Views: 2,015
BGM
10-21-2011, 12:14 PM
56. ### Sample Space of Beta Distribution.

I was wondering something about the Sample Space of the Beta Distribution. this holds for 0 < x < 1 and a,B > 0. And the Sample Space would be...

• Replies: 3
• Views: 3,099
10-21-2011, 10:59 AM
57. ### normal approx / continuity correction

One statistic used to assess professional golfers is driving accuracy, the percent of drives that land in the fairway. Driving accuracy for PGA...

• Replies: 2
• Views: 4,219
10-21-2011, 10:37 AM
58. ### Chi Square Test-Who's correct? Me or Prof

You are instructed to prepare 3 different types of pastry, all containing 16 blueberries per pastry. 6 customers approach you to complain that there...

• Replies: 1
• Views: 3,188
10-20-2011, 05:25 PM
59. ### Likelihood Function.

Hi guys, i have this problems and I need some help to solve it: Optional problem : 1. Let Y be a Bernoulli random variable with parameter p. You...

• Replies: 2
• Views: 3,854
BGM
10-20-2011, 01:40 PM
60. ### Homework Help with continuous probability distributions

Hi if anyone can help me on these two problems, i would really appreciate it. i'm looking at my notes and txtbook, but still don't understand it. ...

• Replies: 1
• Views: 7,941
BGM
10-19-2011, 11:52 PM

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