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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: 30,175
09-30-2005, 09:44 AM
1. ### Poisson Process

I got a question. Q) Let {X(t), t>=0} and {Y(t), t>=0} be independent Poisson processes with parameter (lambda)_1 and (lambda)_2 respectively....

• Replies: 2
• Views: 3,630
11-03-2010, 12:24 PM
2. ### Erlang

Suppose S~Erl(n,lamda) Show that if n>1, then E(1/S) = lamda/(n-1), and if n>2, Var(1/S) = lamda^2/[(n-1)^2*(n-2) Conclude that is Y=(n-1)/S and...

• Replies: 2
• Views: 2,539
11-03-2010, 11:18 AM
3. ### help with beta distribution

for this question How do i show that X1~Beta(a1,a2+a3) whats a hint to show this?

• Replies: 5
• Views: 4,230
11-02-2010, 06:35 PM
4. ### CDF problem

Problem - Let X be a random variable with c.d.f. F(x). Find the c.d.f. of aX + b first for a > 0, then for a < 0. (for a > 0) F(x) = P(X <= x) ...

• Replies: 8
• Views: 8,043
11-02-2010, 04:24 PM
5. ### P value probabilites by hand/T chart

Thank you for taking the time to read my query. I appreciate it. I moved my query from statistics to probability because I really didn't get an...

• Replies: 0
• Views: 4,534
11-02-2010, 01:59 PM
6. ### probability-inequality

let X_1,X_2,.... be a sequence of i.i.d. random variables each with mean 4 and variance 4. show that for large n, 0.5<P<0.9 help needed....

• Replies: 2
• Views: 2,538
BGM
11-02-2010, 10:05 AM
7. ### !!!URGENT!! convolution problem

a signal x(t)=delta(t) is filtered by the filter f(t)=u(t)-u(t-1) multiple times. *compute and plot the result of the first and second application...

• Replies: 0
• Views: 2,495
11-02-2010, 12:42 AM
8. ### change of variable help

1. Let X~Geometric(1/4), and let Y have probability function: pY(y)= 1/6 if y=2 1/12 if y=5 3/4 if y=9 0 otherwise Let W=X+Y. Suppose X and...

• Replies: 1
• Views: 2,420
11-01-2010, 07:53 PM
9. ### CDF - Cauchy distribution

Suppose that a particle is fired from the origin in the (x, y)-plane in a straight line in a direction at a random angle theta(the symbol with the...

• Replies: 3
• Views: 7,329
11-01-2010, 05:59 PM

Hello, I would like to know if someone can help for the question as below? Suppose that P(E) is 0 or 1, show that E is independent of all...

• Replies: 11
• Views: 3,831
11-01-2010, 12:25 PM
11. ### Poll: Basic Probability 3

Please help me with this question Two cards are drawn at random from a pack of cards. Find the probability that both cards are of Red Colour or...

• Replies: 6
• Views: 3,830
BGM
11-01-2010, 12:06 PM
12. ### cdf and pdf

consider the following cumulative distribution function F(x) = 0, x<0 =\frac{x+k}{5}, k\leq x<k+1, k=0,1,2 =1, x\geq3 find P(X=j) for all...

• Replies: 9
• Views: 3,304
BGM
11-01-2010, 12:03 PM
13. ### Exponential Distribution Lifetime problem

The average lifetime is 10 hours = 1/lambda Lambda = 1/10 Find the probability of 2 independent items with average lifetime >= 11 hours. ...

• Replies: 3
• Views: 4,909
11-01-2010, 10:32 AM
14. ### 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: 7,725
11-01-2010, 07:15 AM
15. ### Poll: Basic Probability 2

Four Coins are tossed together. What is probability that HEAD will appear on at least on of the four coins?

• Replies: 6
• Views: 3,140
11-01-2010, 03:28 AM
16. ### help with dirichlet distribution

I am stuck on this problem I have to prove its a density I can do it by show it by integrating it twice with respect to X2 and X1 and it...

• Replies: 11
• Views: 3,907
10-31-2010, 06:15 PM
17. ### Please assist with issue

Decide whether the experiment is a binomial experiment. If it is not, explain why. Each week, a man plays a game in which he has a 41% chance of...

• Replies: 2
• Views: 3,010
BGM
10-31-2010, 03:45 PM
18. ### PDF problem

Suppose X has uniform distribution on (-1, 1). Find the PDF of Y = X^2. OK, without putting all the details... I got for F(y)...P(-square root...

• Replies: 1
• Views: 4,346
BGM
10-31-2010, 03:42 PM
19. ### help with simulating distributions

For each of the following c.d.f F, find a formula for X in terms of U, such that if U~Uniform, then X has c.d.f F. a) F(x) = 0 if x<0 x if...

• Replies: 0
• Views: 2,264
10-31-2010, 01:10 PM
20. ### Distribution of the Sum of r.v.

Guys, I will appreciate if you can give me some hints on this problem: Let X1,X2,...Xn be i.i.d with mass function f(k)= / for k>1. Find the...

• Replies: 6
• Views: 2,745
10-31-2010, 12:00 PM
21. ### Gambler's Ruin problem

I have a question about Gambler's ruin. Consider a Gamber's ruin with initial fortune a and b (a>10, b>10) for players I and II, respectively. Let p...

• Replies: 2
• Views: 3,587
10-31-2010, 11:52 AM
22. ### Interesting Bean Problem

Good evening, I've encountered an interesting problem and need a little help with it (: Question 1A) A bean is placed in a bag. The bean is...

• Replies: 6
• Views: 5,416
10-29-2010, 11:38 PM
23. ### Basic Probability

6 Boys and 6 Girls sit in a row at random. Find the probability that the boys and girls sit alternately. Please help me with steps to calculate in...

• Replies: 9
• Views: 4,026
10-29-2010, 03:58 PM
24. ### Moment Generating Function

Hi all, I'm supposed to find the MGF of the Gamma Distribution. Here is a link to my solution:...

• Replies: 3
• Views: 5,349
BGM
10-29-2010, 01:22 PM
25. ### Estimating the number of red balls drawn

Assume that there are N jars numbered 1 to N. Each jar contains many balls. Assume that we draw a ball from i-th jar. The probability of drawing a...

• Replies: 4
• Views: 3,729
BGM
10-29-2010, 02:29 AM
26. ### Uniform Dist

Suppose X,Y are uniformly distributed over the unit circle. Let R = sqrt(X^2 + Y^2) and theta=arctan(Y/X). What is the joint pdf of (R, theta)?...

• Replies: 1
• Views: 5,635
BGM
10-28-2010, 07:24 AM
27. ### Questions I Missed

When sampling is done for the proportion of defective items in a large shipment, where the population proportion is 0.07, and the sample size is 200,...

• Replies: 3
• Views: 3,903
10-28-2010, 06:07 AM
28. ### Transition Probability Matrix

The 6 faces of a fair die are marked with the numbers 1,2,3,4,5,6. We roll the die repeatedly and independently, noting the numbers that come up. We...

• Replies: 3
• Views: 7,506
10-27-2010, 09:32 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: 6,271
10-27-2010, 09:12 PM
30. ### Chebshev Inequality

Hi! I have the following problem: Suppose X ~ Poisson (Lambda). Show P(X > 2lambda) =< 1/lambda So I wrote out Chebshev's by definition: ...

• Replies: 0
• Views: 2,404
10-27-2010, 03:30 PM
31. ### Jump Discontinuities in CDF's

There aren't any examples of cumulative distribution functions with discontinuities in my textbook. I'm wondering what to do with something like...

• Replies: 4
• Views: 6,038
10-27-2010, 12:33 PM
32. ### Hypergeometric, Binomial, & Integration

I need a lot of help with a few difficult problems. Is anyone here a tutor? I am willing to pay.

• Replies: 0
• Views: 2,240
10-26-2010, 09:22 PM
33. ### Poisson/Phone Call question...

Hopefully, this is my last question before my exam tomorrow at 2pm... Phone calls arrive at a rate of 1 per second(the mean = 1/lambda). Find...

• Replies: 2
• Views: 3,433
10-26-2010, 06:54 PM
34. ### 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: 2,999
10-26-2010, 03:14 PM
35. ### Continous distribution question

X ~ Uniform(0, 10). Find the distribution of Y = 3X + 5 I saw this in my classnotes, but my prof didn't do this during one of the lectures. ...

• Replies: 1
• Views: 2,442
10-26-2010, 02:11 PM
36. ### Probability of 4 of n shots hitting.

Hello. First timer here, hopefully you guys can help me! First of all, let me say that this is not a homework problem of any sort, it's for a...

• Replies: 6
• Views: 3,724
10-26-2010, 01:18 PM
37. ### Question about finding sum of 3 largest rolls of die

The S sum of all 4 rolls = 14 The E(M) minimum value of 4 rolled die is 1.755 The example here my professor worked out for the Expected Sum of...

• Replies: 2
• Views: 3,238
BGM
10-26-2010, 12:21 PM
38. ### Poisson - question how in setting this up

Not asking how to do it, but setting this up I'm having trouble with. Suppose 2,000,000 raindrops land on a roof every second. The area of the...

• Replies: 2
• Views: 2,372
BGM
10-26-2010, 12:12 PM
39. ### Cumulative Distribution Function

Please help me, I have 2 cases: 1. n is positive constant and defined by function f(x)=1/2.n.e^(-n.x) if x>=0 and f(x)=1/2.n.e^(-n.x) if x<0....

• Replies: 8
• Views: 10,152
10-26-2010, 01:37 AM
40. ### help randoooomly chooooose

Hello Everyone, I have :confused: question: Define ni to be the number of families with i children, i = 1,2,3,…..,k. Define E to be the event...

• Replies: 4
• Views: 3,495
10-25-2010, 05:32 PM
41. ### Name of this density function

f(x|theta) = (1+theta)*x^(theta) , where x is in and theta > -1 Hey! I am just trying to figure out which distribution this density function is....

• Replies: 2
• Views: 2,452
10-25-2010, 03:16 PM
42. ### Line Segment Probability

Question: Divide the line segment into 3 parts by selecting 2 points at random from . Find the probability that the largest part is at least 2...

• Replies: 0
• Views: 3,503
10-25-2010, 02:12 PM
43. ### Variance of the sample variance

I am looking to compute the variance of the sample variance. I found a site that does this for the biased sample variance (i.e. 1/n rather than...

• Replies: 2
• Views: 8,251
10-25-2010, 10:39 AM
44. ### Probability split deck of cards

Hi there, I've been stuck in this problem for some time, id be helpful if someone help me shed some light on it. Say we split a deck of 52 shuffled...

• Replies: 3
• Views: 6,008
BGM
10-25-2010, 05:51 AM
45. ### Expected value

Hi, can someone please have a look at my answer? Thanks In advance. A patient presents to you for a consultation regarding a choice between...

• Replies: 0
• Views: 2,730
10-25-2010, 04:35 AM
46. ### How do I simplify this?

(b / (b + w) ) * ((b-1) / ((b-1) + w)) * ((b-2) / ((b-2) + w)) * ((b-3) / ((b-3 + w)) the problem pretty much states without replacement, the...

• Replies: 2
• Views: 3,839
10-24-2010, 10:58 PM
47. ### Sequence of chess games

Person A and Person B play a sequence of chess games. S=(A wins a game) and the outcomes of the successive games are independent with P(S)=P(F)=0.5...

• Replies: 9
• Views: 5,682
10-24-2010, 07:25 PM
48. ### PDF problem, a rather complex one

This isn't a homework problem, but a review problem my prof gave us for the test on Wed... A fair die is rolled. Let X be the highest power of 2...

• Replies: 1
• Views: 3,104
10-24-2010, 03:33 PM
49. ### Events A and B with complements

Hi all, I will show the quest first and my work after. Given: P(A) = 0.3, P(B) = 0.8, P(AUB) = 0.9 A) Find P(A|B), P(A'nB), P(B'UA') B)...

• Replies: 1
• Views: 20,594
BGM
10-24-2010, 01:39 PM
50. ### how do u work out this problem?

Hi There, there is one problem that is killing me. I will appreciate any help. From what I’ve learnt so far it relates to Binomial distribution. ...

• Replies: 1
• Views: 3,962
10-24-2010, 11:12 AM
51. ### Condtional Probability

edit: got it.

• Replies: 1
• Views: 1,844
10-23-2010, 10:31 PM
52. ### Chebyshev's Inequality

We recently had a test question (that I got counted correct) but which I feel like my answer is inadequate. We were told to use the Chebyshev's...

• Replies: 2
• Views: 3,778
10-23-2010, 08:37 PM
53. ### Normal Approx problem(u, Var)

This is a homework problem from last week - I had it figured out last week before I turned it in(and the answer in the back of the book confirmed...

• Replies: 3
• Views: 7,319
10-23-2010, 02:31 PM
54. ### Lottery

15. A group is selling 1000 raffle tickets. The winning ticket gets \$50,000. a. If tickets are given away for free, what is the Expected Value...

• Replies: 6
• Views: 3,482
10-23-2010, 07:19 AM
55. ### Demorgans?

I have to show the following hold. i) (A U B)' = A' & B' ii) (A & B)' = A' U B' Can someone verify if this thinking is correct? i) x is...

• Replies: 2
• Views: 2,391
10-22-2010, 06:31 PM
56. ### Bayesian inference -(unknown mean and variance | and a proof)

hello, i take a bayes lesson. there are 3 questions as my homework, i did one of them. i am new to statistics, so instructor said i can get help as...

• Replies: 4
• Views: 5,065
10-22-2010, 05:07 PM
57. ### standard deviations in scatter plots

I am working with data that involves blood volumes in the heart according to gestation. I have plotted these values using a twoway scatter graph. I...

• Replies: 1
• Views: 6,598
10-22-2010, 01:16 PM
58. ### converges almost surely

I need to use this lemma for my prove, and I dont know how to prove this lemma. "X_n \rightarrow 0 a.s iff for all \epsilon > 0, P(|X_n| > \epsilon...

• Replies: 0
• Views: 2,671
tup
10-22-2010, 01:08 PM
59. ### converges in prob

Let X_1, X_2, ... be independent with P(X_n = 1) = p_n and P(X_n = 0) = 1- p_n. Show that (i) X_n \rightarrow 0 in probability iff p_n \rightarrow 0,...

• Replies: 2
• Views: 2,159
tup
10-22-2010, 12:39 PM

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