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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: 30,315
09-30-2005, 09:44 AM
1. ### 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: 6,680
10-22-2010, 01:16 PM
2. ### 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: 6,679
01-18-2012, 11:22 AM
3. ### Textbook Problem. Calculate E(Y2/Y1)

Joint Probability Density Function: f(y1, y2) = 1/8 * y1 * e^(-1/2 * (y1 + y2)) where 0 < y1 < infinity and 0 < y2 < infinity (0 otherwise) y1 + y2...

• Replies: 2
• Views: 6,663
10-13-2009, 11:30 AM
4. ### factorial.. with replacement?

Here is the problem.. (literally..) In your stats class, the teacher has three drawing for prizes (a, b , c). There are 15 students in class ...

• Replies: 2
• Views: 6,660
03-01-2006, 07:35 AM
5. ### Question about exponential distribution

Okay, because P(Y) is an exponential function with mean of 10, I know a=1, B=10 P(Y) = (1/B)e^(-y/B), or (1/10)e^(-y/10). I'm stuck with what to do...

• Replies: 3
• Views: 6,641
BGM
11-16-2011, 12:00 AM
6. ### unfair coin problem

im stuck with a part of a problem which is : An unfair coin (p{h}=p=0.6) is tossed n=20 times. FIND the probability that the number of heads k is...

• Replies: 8
• Views: 6,640
09-14-2010, 01:46 AM
7. ### real estate probability

A real estate agent is showing homes to a prospective buyer. There are 12 homes in the desired price range listed in the area. The buyer has time...

• Replies: 1
• Views: 6,624
07-11-2009, 08:03 AM
8. ### The auto-correlation of poissonian point process

I saw in a paper that the autocorrelation function of a poissonian point process is the following, R(t)=v^2+v*delta(t), written in Matlab style. The...

• Replies: 2
• Views: 6,620
04-29-2014, 02:00 PM
9. ### Distribution of Sum of Independent Random Variables Having Chi-square Distributions

Hey... Ive been asked to Prove or show that one of the properties of the Chi-square distribution is true and I have no idea how to even get started....

• Replies: 1
• Views: 6,610
02-04-2009, 09:13 PM
10. ### Transformation of Y = 1/X

X ~ U(2,4). Find the density of Y = 1/x f(x) = (1/2, 2<x<4) (0,elsewhere) G(Y) = P(Y<y) = P(1/X<y) = P(X>1/Y) = 1 -...

• Replies: 3
• Views: 6,604
11-07-2008, 06:45 AM
11. ### joint pdf question

I'm not quite sure if I'm approaching this question right... If the joint probability density of X and Y is given by f(x, y) = 24y(1 - x - y)...

• Replies: 1
• Views: 6,584
10-28-2009, 09:30 PM
12. ### Help with a probability problem

There were three parts to the following problem I solved with no problem but part D I can't figure out for the life of me. Can anybody offer any...

• Replies: 2
• Views: 6,571
BGM
09-27-2010, 12:16 PM
13. ### Traffic light probability question.Need help!!

Hi, Need help to solve this probability question. At a certain traffic signal red for 30 seconds, yellow for 5 seconds, and green for 25 seconds....

• Replies: 2
• Views: 6,569
08-29-2014, 11:10 AM
14. ### joint distributions, marginals, conditional

I am trying to teach myself joint distributions. I've been struggling with how to know what limits of integration to use when finding the marginal...

• Replies: 0
• Views: 6,568
03-09-2009, 12:11 PM
15. ### probability from moment generating function?

if the moment generating of a random variable X is M_x(t)=(1-t)^-2 compute P(-2 < X < 3) or explain why it cannot be computed how do I do...

• Replies: 4
• Views: 6,564
04-10-2009, 08:27 AM
16. ### 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: 6,554
12-13-2011, 09:03 PM
17. ### probability of alleles (?)

Each of us has an ABO blood type, which describes whether two characteristics called A and B are present. Every human being has two blood type...

• Replies: 2
• Views: 6,543
10-12-2009, 01:59 PM
18. ### Help with probability..asap plz

An entomologist is studying the effect of a chemical sex attractant (pheromone) on insects. Several insects are released at a site equidistant from...

• Replies: 5
• Views: 6,543
10-01-2010, 05:30 AM
19. ### exact probability, two random variables, normal distribution

Hi, I've been stuck on this problem for awhile: The problem asks to find the exact probability that X will last longer than Y. It says that on...

• Replies: 3
• Views: 6,534
03-08-2010, 10:30 PM
20. ### Point (X,Y) is picked inside square

I saw this problem and we have gone over joint probability but I searched all over my textbook and could not find a problem similar. A point (X,Y)...

• Replies: 9
• Views: 6,532
11-09-2010, 12:26 PM
21. ### Counting probability given the mean and standard deviation

Hi all :-) I'm trying to find solution to the following problem, could anyone please help ? In response to the increasing weight of airline...

• Replies: 3
• Views: 6,525
01-17-2012, 04:23 PM
22. ### Standard Normal Distribution z0

I am a beginning student in Statistics. I don't understand the concept of z0, such as "find z0 such that P( -1.2 < z < z0 ) = 0.8671". It's not...

• Replies: 1
• Views: 6,515
03-05-2008, 01:37 PM
23. ### Poisson process, order statistics problem

Starting at some fixed time, satellites are launched at times of a Poisson process with rate lambda. After an independent amount of time having...

• Replies: 1
• Views: 6,509
BGM
09-03-2010, 06:55 AM
24. ### How to draw tree diagram

I have the following problem from my home problem. An oil-prospecting firm hits oil or gas on 10% of its drillings. If the firm drills two wells,...

• Replies: 1
• Views: 6,505
03-07-2010, 05:53 PM
25. ### 2 randomly selected have same birthday

Please help to answer the following question with detailed steps: What is the probability that two randomly selected people have the same...

• Replies: 2
• Views: 6,502
01-24-2009, 06:51 PM
26. ### n-dimensional normal distribution

Hi. My question is about the theory. For example we have two independent normal distributed variates. Then their joint distribution is also...

• Replies: 3
• Views: 6,500
12-17-2009, 11:39 AM
27. ### help?

11.32: To estimate the mean height u(mew) of male students on your campus, you will measure an SRS of students. You know from gov't data that the...

• Replies: 2
• Views: 6,494
02-09-2009, 04:08 PM

I can't figure these 2 problems out. I'm not very good at stats, so they might be easy. Please answer, even if you only know one of them or part of...

• Replies: 10
• Views: 6,493
10-28-2008, 03:06 AM
29. ### homework help: how do I solve this without standard deviation? hypothesis testing

Q7. Law enforcement officers in a city have claimed that over 40% of all robberies committed by those who have a history of drug abuse and/or alcohol...

• Replies: 0
• Views: 6,490
05-07-2009, 06:48 AM
30. ### false positive

A company has developed a new drug screening test which correctly identifies cocaine users 97% of the time; marijuana users 88% of the time and other...

• Replies: 3
• Views: 6,489
09-21-2010, 03:53 AM
31. ### I think I did this right

If x, the time (in minutes) to complete an change job at certain auto service station, is uniformly distributed over the interval 20 to 30,...

• Replies: 1
• Views: 6,478
BGM
11-02-2012, 02:23 PM

Hi im having trouble with this question. If anyone could help me out thatd be great , Im not sure where to start! Heres info: The cost of...

• Replies: 21
• Views: 6,469
03-30-2008, 10:38 PM
33. ### Probability | Card deck

A card is drawn from a well shuffled deck of 52 cards. Find P(drawing a face card or a 4). Now since the cards can't be replaced, would you get...

• Replies: 1
• Views: 6,447
03-22-2011, 01:58 AM
34. ### Baye's Theorem

Hi, I have two questions that I am struggling with, that concern the Baye's Theorem.... 1) Mr. Smith's gardener is not dependable; the probability...

• Replies: 1
• Views: 6,428
11-13-2006, 05:01 AM
35. ### Weird Probability Problem

Hi, I'm having trouble with a problem assigned by my teacher that reads: "Assume that you are boarding a flight in which there are five seats and...

• Replies: 5
• Views: 6,422
11-01-2008, 03:49 PM
36. ### Moving window of Standard Deviation

I'm not sure how best to phrase this, so please bear with me: I have a stochastic process from which I can measure one representative value per...

• Replies: 4
• Views: 6,417
12-30-2008, 07:56 PM
37. ### Fishing Probability

The probability that Pete will catch fish on a particular day when he goes fishing is .8. Pete is going fishing 3 days next week. The probability...

• Replies: 1
• Views: 6,415
04-22-2012, 04:17 PM
38. ### null hypothesis questions

A manufacturer of computer memory chips produces chips in lots of 1000. If nothing has gone wrong in the manufacturing process, at most 7 chips each...

• Replies: 6
• Views: 6,411
08-08-2010, 04:44 PM
39. ### zero inflated poisson distribution

I am new and I hope I'm abiding to the rules. I just wanted to know what exactly a zero inflated Poisson distribution is? How is it related to the...

• Replies: 2
• Views: 6,401
03-16-2010, 09:21 AM
40. ### y follows a Poisson distribution with rate lambda*x

Assume that the number of faults in the roll, say y, follows a Poisson distribution with rate lambda*x, where x is the length of the roll. Does this...

• Replies: 4
• Views: 6,386
12-05-2010, 05:27 PM
41. ### Ratio of two independent gamma random variables

Hello, I am working on a problem in which I need to find the expectation of the square root of the ratio of two independent gamma random variables...

• Replies: 5
• Views: 6,384
BGM
01-17-2013, 10:44 AM
42. ### Normal distribution probability density function returning values > 1

i am trying to draw a normal curve over a histogram of some data of mine and i just can't get it to come out right! Mean =1.002327404 Standard...

• Replies: 11
• Views: 6,382
10-03-2008, 04:50 PM
43. ### Stuck on Setting upa problem.

I been having a problem solving this type of question. I have the answers to this along with variations of the same problem, but I am still un able...

• Replies: 1
• Views: 6,378
04-24-2006, 08:57 PM
44. ### Transformation of univariate random variables

Hi all, I need help with two problems: Problem1: Let U and V be iid Uniform(-1,1). Furthermore, let W=U^2 + V^2 and Z = U / sqrt(W). What is...

• Replies: 3
• Views: 6,371
02-08-2010, 08:42 AM
45. ### Joint and marginal pdf

Hello everyone. I need help in the following question: Let the joint distribution of X and Y be given as f(x,y)=2*exp{-(x+y)}, 0<x<y</infty a)...

• Replies: 0
• Views: 6,369
07-05-2009, 12:16 PM
46. ### Help with these probability problems

1. Conditional Prob: Approximately 1/125 of all births are fraternal twins and 1/300 of births are identical twins. Elvis Presley had a twin brother...

• Replies: 1
• Views: 6,366
01-13-2007, 12:58 PM
47. ### Need help please!!

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: 6,365
01-25-2012, 12:31 AM
48. ### Probabilities of Gender Sequences

nCr and nPr doesn't seem to get me anywhere. What the duece?

• Replies: 2
• Views: 6,364
10-04-2006, 02:17 PM
49. ### Hypergeometric distribution

Hi, The problem is- A shipment of 20 cameras includes 3 that are defective. What is the minimum number of cameras that must be selected if we...

• Replies: 1
• Views: 6,360
04-04-2009, 11:49 PM
50. ### Expected value

Hi, have a question about expected value, there is only a few lines my text book regarding this. The prizes that can be won in a sweepstakes are...

• Replies: 2
• Views: 6,352
02-25-2006, 10:50 PM
51. ### Help with Bayesian question please

Just got a question with Bayes problem, I always struggle to understand the actual question in Bayes problems so that could be why I'm stuck, but...

• Replies: 48
• Views: 6,351
07-27-2015, 09:48 AM
52. ### 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: 6,340
01-22-2012, 10:16 PM
53. ### Poisson Distribution

Hi: I was wondering if there is a proof (or reference) for the following property of the Poisson distribution: Go here, ...

• Replies: 2
• Views: 6,335
01-08-2010, 09:54 AM
54. ### help with exponential distribution

X1,X2,...,XN are independently identically exponentially distributed with expected value of 5. How can I compute Xn when n=20 and N=1000? Then...

• Replies: 7
• Views: 6,332
11-30-2010, 12:13 AM
55. ### Conditional Expectation question

My final is on Mon, and I got this HW problem wrong from last week, and I still don't understand why. An item is selected randomly from a...

• Replies: 6
• Views: 6,329
12-21-2010, 07:11 AM
56. ### Help with Confidence Intervals

The questions regarding confidence intervals and population means are hard to understand: Please help me set them up in a formula and solve. #3 ...

• Replies: 4
• Views: 6,322
09-26-2005, 10:01 AM

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: 6,321
10-27-2010, 09:12 PM

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