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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: 30,210
09-30-2005, 09:44 AM
1. ### 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: 7,755
11-01-2010, 07:15 AM
2. ### Indicated probability

Assume that X has a normal distribution, and find the indicated probability. The mean is μ = 15.2 and the standard deviation is σ = 0.9. Find the...

• Replies: 1
• Views: 7,745
BGM
12-12-2010, 03:16 PM

Hello everyone... I really need ur help in solving these questions.. 1) Two cards are randomly drawn from a deck of 52 playing cards. Find the...

• Replies: 3
• Views: 7,734
02-20-2009, 10:46 AM
4. ### Help! - Probability Problem

I need some help with this one: A company is considering implementing one of two quality control plans for monitoring the weights of automobile...

• Replies: 1
• Views: 7,723
04-18-2006, 06:48 AM
5. ### Expected value and confidence interval for non-normally distributed discrete variable

Greetings, Say I pull 11 random independent samples from a population and they take on the following values (assume that these are the only values...

• Replies: 3
• Views: 7,704
07-04-2011, 02:35 PM
6. ### Expected value, variance, standard deviation

I am kind of stuck :confused: Problem: A random variable X has the distribution: px = ( 0 1 2 4 ) ...

• Replies: 3
• Views: 7,681
12-04-2006, 11:02 PM
7. ### How do I get pmf from a table of cdf?

If I have a cdf table looks like this. How do I calculate the respect pdf? cdf X,Y 1 2 3 1 a b c 2 d e f...

• Replies: 1
• Views: 7,641
01-11-2009, 10:06 PM
8. ### Sampling Probability

Hi, Can anyone help with this problem: If i have a given volume (v) that contains a number of discrete particles (p) randomly distributed...

• Replies: 10
• Views: 7,640
06-29-2010, 07:29 AM
9. ### probability question

Hello, I am having trouble with my stat homework. Maybe someone can give me some guidance? I would really appreciate it! A woman is fishing for...

• Replies: 17
• Views: 7,637
10-28-2008, 04:23 PM
10. ### total demands in the next two weeks (normal distribution)

Hi guys. Problem: The weekly demand for a product approximately has a normal distribution with mean 1,000 and standard deviation 200. The...

• Replies: 2
• Views: 7,635
06-30-2011, 01:14 AM
11. ### HELP PLEASE! Normal Probability Question.

So I have a quick question. I was able to figure part A out (i think) but I don't think my answer for part B is correct... The daily dinner bills...

• Replies: 2
• Views: 7,606
03-27-2010, 05:13 PM
12. ### Homework Question Need Help ASAP

I have a homework problem that I am really stuck on and unfortunately it is due by wednesday so I am hoping someone can help me out. Here it goes: ...

• Replies: 1
• Views: 7,605
11-28-2006, 09:11 AM
13. ### 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: 7,590
02-05-2012, 10:32 PM
14. ### Conditional probability with Binomial distribution

Hello all I am trying to make a calculation here, and the result doesn't make sense to me, I don't know what I am doing wrong... I have a...

• Replies: 4
• Views: 7,588
08-15-2013, 03:27 PM
15. ### Confidence interval for binary data

Hi, I've got binary data (0 & 1's) which I represent as a average along a variable "speed". E.g. when speed is 5, the data is and I present that by...

• Replies: 0
• Views: 7,558
07-14-2009, 12:03 PM
16. ### 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: 7,542
01-26-2012, 11:32 AM
17. ### Consequences of choosing the wrong likelihood function...

hey everyone! just a quicky-quick question here. i think i remember reading somewhere that some of the nice properties of parameter estimates...

• Replies: 26
• Views: 7,532
09-23-2012, 12:17 PM
18. ### Moment Generating Function of a Chi-Squared distribution

Hey guys, need help with this question. Random Variables V and U are independent with N~(0,4). Let W = U^2 + V^2 . Calculate P(W>24). Is the...

• Replies: 20
• Views: 7,529
05-09-2012, 01:54 AM
19. ### 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: 7,528
10-27-2010, 09:32 PM
20. ### [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: 7,519
01-29-2012, 11:08 PM
21. ### Joint density function

This is from Exercise 5.26 from Mathematical Statistics with Applications v6. f (y1, y2) = {2, 0 <= y1 <= 1, 0 <= y2 <= 1, 0 <= y1 + y2 <= 1 ...

• Replies: 17
• Views: 7,514
04-22-2008, 05:15 PM
22. ### Conditional Probability

To reduce theft, the ABCD Company screens all its employees with a lie detector test that is known to be correct 90 percent of the time (for both...

• Replies: 0
• Views: 7,509
10-30-2005, 11:59 PM
23. ### Bayes theory interview question.

This question is a typical interview question at a job I am currently seeking. The reason I am posting it is I have had different answers from...

• Replies: 3
• Views: 7,493
09-12-2012, 08:45 PM
24. ### Gamma Distribution parameters

Hi, I'm trying to understand the theory behind the probability distributions specifically what do the shape and scale parameters for gamma...

• Replies: 4
• Views: 7,492
BGM
09-28-2010, 01:14 AM
25. ### 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: 7,491
BGM
01-19-2012, 01:55 PM
26. ### probability

This is a part of a problem. I decided to ask it here after hours of trying to solve it... Two tennis players make a match composed of 5 sets....

• Replies: 17
• Views: 7,476
11-30-2005, 04:49 PM
27. ### Prove or Dispprove Independence Statement

Hey, "If A is independent of B and B is independent of C, then A is independent of C. Prove this statement or give a counterexample if it is...

• Replies: 1
• Views: 7,462
01-16-2013, 07:35 PM
28. ### Gamma Probability (really an area of a circle question)

The question reads: Explosive Devices used in mining operations produce nearly circular craters when detonated. The radii of these craters are...

• Replies: 1
• Views: 7,460
BGM
02-18-2010, 09:20 AM
29. ### 97th percentile

"suppose the moisture content per pound of a dehydrated protein concentrate is normally distributed with a mean of 3.5 and standard deviation of 0.5....

• Replies: 5
• Views: 7,444
03-26-2012, 10:34 PM
30. ### Probability of getting 3 out 5

I am driving myself up the wall. I am trying to figure out the probability of getting 3 out of 5 questions right. At first my thougt was 1/5 x 1/5 x...

• Replies: 1
• Views: 7,442
09-11-2009, 10:48 AM
31. ### I had 100 question and I am stuck with the following 7 questions! Help

Suppose the fill amount of bottles of soft drink has been found to be normally distributed with a mean of 2.0 liters and a standard deviation of...

• Replies: 1
• Views: 7,439
11-07-2005, 02:46 PM
32. ### distribution of the range of N independent standard normal variables

Let x1, x2, ... xn be independent standard normal variables. (standard normal: normal with 0 mean and variance 1). Let the range R be defined as...

• Replies: 4
• Views: 7,428
02-20-2010, 01:07 AM

Hi, I've got a probability problem that has had me stumped all weekend. Can anybody please help? Suppose that two balanced dice are tossed...

• Replies: 1
• Views: 7,426
07-03-2007, 12:20 PM
34. ### Joint Density Function Question

So (fy1,fy2) = e^-(y1 + y2) ) , for y1>0, y2>0 and 0 elsewhere. What is P(Y1 + Y2 < 3) The answer is .8009 I just can't work out how to get...

• Replies: 4
• Views: 7,397
02-21-2010, 08:52 AM
35. ### Conditional probability calculation

Please can someone help me with the following question: An urn contains 3 white, 6 red and 5 black balls. Six of these balls are randomly selected...

• Replies: 1
• Views: 7,397
BGM
08-08-2011, 11:16 AM
36. ### Fairly Easy Question - Poisson Distribution

My first post! Anyway I just need a bit of help with a question that I've come across in a textbook which is as follows: Cars arrive at a toll...

• Replies: 5
• Views: 7,391
02-11-2010, 10:48 PM
37. ### Type II error

I'm currently doing a statistics assigment. In one of the questions, i've been asked to "discuss" what the probability of a Type II error, what i...

• Replies: 10
• Views: 7,387
10-12-2008, 10:47 AM
38. ### Binary Bootstrap

Is it valid to use a bootstrap technique for estimating variance in a binary (yes/no or 1/0) data set? My motivation for doing so is to perform...

• Replies: 5
• Views: 7,384
09-29-2009, 04:01 AM

A statistical analysis of 1,000 long-distance telephone calls made from the headquarters of the Bricks and Clicks Computer-corporation indicates that...

• Replies: 1
• Views: 7,377
04-26-2009, 04:21 AM
40. ### Can I calculate a p-value here?

Hey everyone! Ok so I ran a biochemistry experiment the other day and I wanted to calculate a p-value for my data. The experiment is pretty...

• Replies: 2
• Views: 7,369
04-02-2009, 04:47 PM
41. ### 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: 7,363
11-01-2010, 05:59 PM
42. ### 19 lowercase letters + 1 single digit number = possible combinations ?

Hi everybody and happy new year too all :tup: I've just discovered this forum today and I have one thing to say : AWESOME ! :) I have trouble...

• Replies: 10
• Views: 7,362
01-20-2011, 03:42 AM
43. ### joint probability density function, using the Jacobian

X1 and X2 are independent random variables from a standard normal distribution so the joint p.d.f of X1, X2 = p.d.f X1 x p.d.f X2 = ( 1/(2pi)^1/2)...

• Replies: 4
• Views: 7,359
BGM
11-07-2010, 10:39 PM
44. ### Poisson process, payment, standard deviation

We have an insurance company that pays out claims at times of a Poisson process, with rate 4 per week. Suppose that the mean payment is 10K dollar...

• Replies: 6
• Views: 7,350
09-01-2010, 09:06 PM
45. ### Process capability without variability in data?

My company uses Cpk to judge process capability, with a 1.33 Cpk being the acceptable minimum for most processes. In some cases, we do not have...

• Replies: 5
• Views: 7,348
09-11-2009, 06:41 AM
46. ### 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: 7,337
10-23-2010, 02:31 PM
47. ### why should the I use a t distribution? (theory question)

Hello I would like some help with the theory behind the t-test. I know how to technically perform a t-test but something in the logic doesn't add...

• Replies: 5
• Views: 7,325
BGM
05-19-2010, 01:15 PM
48. ### discrete approximation of a normal distribution

Hi, i have a normal distribution \mu=10, \sigma=1 and need a discrete approximation of it in order to calculate e.g. P(X=8). How can i...

• Replies: 5
• Views: 7,319
04-16-2012, 11:05 AM

Hi all, please i have only one question and I can finish my qestions exam which isdue to morrow,Please , I beg you to help me. Q: The P - value in...

• Replies: 1
• Views: 7,316
09-29-2005, 07:20 PM
50. ### Poisson Distribution Question

I am using the Poisson distribution model the determine the probability of an event occurring. I know that the mean of the event occurring is 7. ...

• Replies: 10
• Views: 7,307
11-01-2005, 12:17 PM
51. ### Probabilities and variable Z

The question was asked... For standard normal random variable Z, find the following probability P(Z=0.74). I looked in my book's table and found...

• Replies: 4
• Views: 7,299
06-10-2012, 05:31 PM
52. ### Scaling covariance and variance

I have the variance and covariances for a number of assets(stocks), and i need to scale them from 1 month to a year. Would it be correct to think...

• Replies: 1
• Views: 7,272
10-14-2010, 12:16 AM
53. ### Poisson distribution and p-value

Does anyone know how to find a general p-value for the poisson distribution. All I have is the expected number of occurrences, given by the poisson...

• Replies: 0
• Views: 7,267
03-18-2008, 01:09 PM
54. ### A simple problem about normal distribution

At supermarkets in a Midwestern city the sales of canned tuna varies from week to week. Marketing researchers have determined that there is a...

• Replies: 2
• Views: 7,242
02-07-2012, 06:01 PM

I'm having a difficult time figuring this out... confused on how to go about solving, & which formula/steps to use.... A population has a mean...

• Replies: 1
• Views: 7,209
10-06-2005, 08:03 AM
56. ### 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: 7,206
12-30-2011, 02:39 PM
57. ### density function

I have a problem that says: If U is uniform on , find the density function of U^2. So far I have that F(y)=sqrt(y) Where do I go from there?? I...

• Replies: 2
• Views: 7,179
02-19-2009, 05:18 PM
58. ### Properties of discrete random variables

Hello, would some one with more experience mind to confirm or correct me: For discrete random variables I know: E = aE+b and...

• Replies: 4
• Views: 7,144
11-28-2010, 12:37 PM

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