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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. ### Uniform distribution on a triangle

Hi All! So happy to find this site! If (x,y) is the value of the random vector (X,Y) and is uniformly distributed over the triangle with vertices...

• Replies: 10
• Views: 12,079
BGM
12-03-2010, 03:38 PM
2. ### differences between one-tailed and two-tailed P-value

I am doing hypothesis testing using t-test and p-value. I calculate my p-value based on the degrees of freedom and the t-test value. The p-value is a...

• Replies: 9
• Views: 12,063
04-12-2010, 09:51 PM
3. ### approximating binomial distribution w/ normal distribution

Hi all, I'm stuck on the following problem: The percentage of fat in the bodies of American men is an approximately normal random variable with...

• Replies: 2
• Views: 11,988
06-25-2008, 06:45 PM
4. ### Binomial Distribution

I really need help with this homework. I've been on one question for over an hour. The Question is The rates of on-time flights for commercial...

• Replies: 9
• Views: 11,972
03-05-2012, 07:24 PM
5. ### Expected Value of pmf

I am currently preparing for my upcoming actuary p/1 exam. The following question was in an book I am using:...

• Replies: 4
• Views: 11,958
06-26-2009, 04:09 PM
6. ### standard deviation of a ratio of dependent variables

Hi- I have a function (ratio essentially) r= x / (1-x) I need some way of expressing the error of r ... I've experimentally measured x and...

• Replies: 2
• Views: 11,908
11-27-2008, 04:54 AM
7. ### Anderson-Darling test appropriate?

Hi, I have a large (>2500) number of z-scores and I want to test if the distribution of these deviates from a unit normal distribution. I have...

• Replies: 6
• Views: 11,851
10-17-2010, 10:04 PM
8. ### If X ≤ Y, then E(X) ≤ E(Y)

There is a theorem that says: "Let X and Y be random variables. If X ≤ Y, then E(X) ≤ E(Y)." But I don't really understand the meaning of "X ≤...

• Replies: 3
• Views: 11,831
07-08-2009, 09:09 PM
9. ### What is the process spread ?

Here's the question: Fifty measurements were taken to determine the weights of filled ice cream containers. The average of these measurements is...

• Replies: 2
• Views: 11,819
07-23-2008, 07:12 AM
10. ### Probability density function

I have a problem on one part of the four parts of this question. Here it is: The probability density function of the time customers arrive at a...

• Replies: 5
• Views: 11,809
10-08-2010, 03:00 PM
11. ### Dirichlet distribution - moments (mean and variance)

For a Dirichlet variable, I know the means and covariances, that is, E = \alpha_i/\alpha_0 Cov =\frac{ \alpha_i (\alpha_0 I -...

• Replies: 12
• Views: 11,806
02-14-2012, 10:56 AM
12. ### Is it binomial probability?

Affirmative action commitments by industrial organizations have led to an increase in the number of women in executive positions. Satellite Office...

• Replies: 1
• Views: 11,771
10-30-2009, 08:36 PM
13. ### deriving expected value of negative binomial distribution

Hey all, I've derived the expected value of the binomial distribution, but I can't seem to figure it out for the negative binomial distribution....

• Replies: 0
• Views: 11,759
05-13-2007, 07:50 PM
14. ### Integrating a probability out

I really do not know & understand about integrating out a probability, in fact I really do not understand the phrase integrate something out. The...

• Replies: 2
• Views: 11,735
09-25-2010, 01:47 PM
15. ### Beginning Bayes problem

I'm getting about every other question right, and since the back of the book only has answers, not whole solutions, I can't tell what I'm doing...

• Replies: 1
• Views: 11,687
09-27-2006, 06:24 PM
16. ### Probability question

I read the sticky in this section about trying the problem before posting the question but I don't know where to begin on this problem. Any help...

• Replies: 14
• Views: 11,658
04-03-2011, 04:15 PM
17. ### Figure out if there is any statistical significance

Hi - I have some data on the internal temperature of cooked meat. The meat patty is a failure if the temperature obtained is below a certain...

• Replies: 8
• Views: 11,646
06-10-2010, 01:27 PM
18. ### Binomial Distribution Analysis Question

Hi everyone. I have a couple of questions and would greatly appreciate it if you could help me out! First, I'll provide some information: ...

• Replies: 4
• Views: 11,622
07-07-2012, 12:07 PM
19. ### Probability of radar detection

Aircraft is in certain area, radar correctly registers its presence with prob. of 0.95. If it is not present, radar falsely registers its presence...

• Replies: 16
• Views: 11,460
10-11-2010, 02:39 PM
20. ### Math Symbols - R1 --> R2

What does the symbol R mean in the following description: "Let X be a discrete random variable, and let g : R^1 -> R^1 be some function ... " ...

• Replies: 4
• Views: 11,448
10-07-2012, 12:34 AM
21. ### 2 four sided dice, probability of 1 dice = 3, sum = even

2 four tetrahedral dice with sides, 1,2,3,4. the two dice are thrown, what is the probability that given the first dice is a 3, the sum of the 2...

• Replies: 1
• Views: 11,341
04-24-2012, 08:56 AM
22. ### ex(xy)

Hi, i can't figure out how do i calculate e(xy) in cases they are not independent and lets say they have the same distribution, for instant...

• Replies: 1
• Views: 11,322
01-08-2010, 08:36 AM
23. ### simple coin flip problem

hi, I recently discovered this forum and I think this could help me with my stats courses... I havent received the text book yet, so my first...

• Replies: 16
• Views: 11,286
10-23-2006, 09:09 AM
24. ### How to find std. dev. of Probability Distribution using Excel? Help please.

Hello, I can find the Population std. dev. using the formula and my BAII plus calc, but would like to know how to find the same using an Excel...

• Replies: 1
• Views: 11,162
BGM
12-15-2011, 02:26 PM
25. ### Using Taylor expansion for calculating Expected Value

Hello, This question is motivated by a very helpful approach suggested by BGM for solving an expected value estimation problem recently posted on...

• Replies: 1
• Views: 11,097
BGM
04-04-2011, 02:15 PM
26. ### Chebyshev's theorem and empirical rule

can someone please explain how to do this problem? I am so confused! Assume the distribution of weights of US adults are normally distributed...

• Replies: 5
• Views: 11,073
12-10-2008, 02:04 PM
27. ### Lickert scale mean median mode?

How do we find a 5 point lickert scale data`s mean median mode? is it possibl? I am not familiar with lickert scale data analysis, and yet I have to...

• Replies: 6
• Views: 11,046
08-13-2010, 03:36 AM
28. ### Performing a blood analysis

To perform a certain type of blood analysis the lab tech must perform two procedures. First procedures requires either 1 or 2 steps and the secound...

• Replies: 1
• Views: 10,993
10-09-2005, 04:41 PM
29. ### Normal Distribution

An individuals’ heights are normally distributed with mean 70 and standard deviation 3 (inches). a) What proportion of the population is...

• Replies: 4
• Views: 10,981
04-24-2010, 01:34 AM
30. ### Symbols in statistics

x^n x to the power of n, x^2 is x squared nPr Permutation, nPr = n!/(n-r)! nCr Combination, nCr = n!/(r!(n-r)!) P(A|B)

• Replies: 0
• Views: 10,958
11-07-2005, 04:11 PM
31. ### MLE of range of Uniform(a,b)

So, I want an MLE for (b - a). log L(a,b|x) = -n log (b - a) given a < x_(1) and b > x_(n) but d/da log L gives me n/(b-a) >, and in fact =/=...

• Replies: 9
• Views: 10,902
03-17-2011, 12:13 PM
32. ### conditional probability

The table below displays data the First Bank of Silverhaven (FBS) has collected on the personal savings accounts of its job-holding customers. The...

• Replies: 3
• Views: 10,891
10-22-2013, 12:40 PM
33. ### Joint probability distribution

1. An instructor has given a short test consisting of two parts. For a randomly selected student, let X = the number of points earned on the rst part...

• Replies: 1
• Views: 10,820
10-11-2009, 07:28 PM
34. ### Prob: Normal probability distribution

The mean cost of domestic airfares in the United States rose to an all-time high of \$385 per ticket (Bureau of Transportation Statistics website,...

• Replies: 1
• Views: 10,757
10-07-2014, 07:39 PM
35. ### Likelihood Ratio Test Statistic

Hi guys, Heres my problem: ********** Data X1,X2,....,Xn, n = 20, are available of numbers of flaws per 10 metres of bales of a manufactured...

• Replies: 5
• Views: 10,569
BGM
03-08-2011, 01:43 AM
36. ### 'Shifted' Poisson Processes?

Hi all. I’m a graduate student in ops research, but my research is in the optimization side of things more so than the stochastic processes. I...

• Replies: 2
• Views: 10,562
BGM
05-18-2013, 03:05 PM
37. ### Find the value of x

I am having trouble finding the value of x with this problem, because my teacher's example problems are a lot different! The question is A new...

• Replies: 1
• Views: 10,555
10-15-2008, 10:18 PM
38. ### Keno or LOTTO style

So, here is how the game goes. suppose that the game uses the numbers 1 through 50 and suppose that the operator selects eight of these. If the...

• Replies: 21
• Views: 10,553
cet
09-27-2006, 04:41 PM
39. ### Probability Help.

Im not sure why I can't figure out these 2 problems. I got the first one right, and I'm using the same thought process to do the other 2, I just...

• Replies: 8
• Views: 10,552
06-15-2012, 06:22 PM
40. ### Prob w/Combination of At Least AND Combination

I'm stuck on this. I've had similar probs, but none that combine the At Least with this type of selection. I really hate to ask for help on a...

• Replies: 5
• Views: 10,441
04-23-2006, 08:38 AM
41. ### Joint probability distribution functions

So a joint pdf is of the form P(X,Y) = SS f(x,y) dx dy, where 'S' is the integral symbol. I've got to cook up the pdf for f(x,y), where X and Y...

• Replies: 3
• Views: 10,395
10-25-2006, 07:34 PM
42. ### Poisson. Calculate expected frequency problem.

I've decided to brush up on my statistics recently by jumping right in the middle of it, and I landed on the normal distribution. I have this...

• Replies: 4
• Views: 10,353
06-15-2009, 09:07 AM
43. ### Is a subset of a normal distribution normal?

An easy one for some of you guys here I suspect. Thanks to anyone who can help me with it. I have an application which adds a normally...

• Replies: 4
• Views: 10,322
10-29-2009, 03:54 AM
44. ### Joint Probability Distribution

Hello all! Having a bit of problems here with making the table for a joint distribution: Question: 3 Fair coins are tossed. Let X = #of heads in...

• Replies: 6
• Views: 10,313
02-27-2009, 07:51 PM
45. ### Match odds versus overall odds of winning in horse racing

The problem I have is as follows. Take a horse race with multiple entrants. Assume that I can accurately assess the probability of horse X...

• Replies: 5
• Views: 10,310
12-10-2008, 02:44 PM
46. ### Dice probability - at least 2 's out of ten

Hi If I roll a fair dice 10 times, what is the probability of getting at least two 6's? edit: Which method shall I use? Say, it's at least 3...

• Replies: 1
• Views: 10,279
12-17-2008, 09:23 PM
47. ### Random probability distribution for demand

Hi All, I have a sample of 100 items with a specific daily expected demand probability. Average demand for a day is 4 (without repetition). I have...

• Replies: 10
• Views: 10,278
12-29-2010, 12:22 PM
48. ### Finding probability with given mean and standard deviation

Hi, I have tried to do this using the z value method but I'm not even sure if I'm right. The question is: "The recommended total blood cholesterol...

• Replies: 4
• Views: 10,264
03-23-2013, 12:42 PM
49. ### Finding E[X] and Var[X] of exponential distribution

Transistors produced by one machine have a lifetime which is exponentially distributed with mean 100 hours. Those produced by a 2nd machine have an...

• Replies: 7
• Views: 10,212
10-19-2010, 12:23 PM
50. ### The Minimum of n Independent Normal Distributions

This is a very good article, on the subject of the distribution of the minimum of several random variables, by Joshua Hill: ...

• Replies: 2
• Views: 10,207
07-10-2010, 03:47 AM
51. ### 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: 10,203
10-26-2010, 01:37 AM
52. ### probability question with percentage of sales

(I accidentally posted this in the statistics forum so I am moving it over here.) I have worked on solving the problem below for over an hour and...

• Replies: 3
• Views: 10,202
02-25-2010, 08:50 PM
53. ### Intercept variable in Excel regression test

Hi, I am running a regression test to see the relationship between free cash flow (FFO) and Stock Price of a few companies, using Excel. (Stock...

• Replies: 3
• Views: 10,195
12-12-2008, 09:20 PM
54. ### Probability question making my brain hurt :p

"suppose you know that a friend of yours has two children and that at least one of them is a boy. One day, you visit your friend's house and his son...

• Replies: 1
• Views: 10,145
03-18-2014, 03:22 AM
55. ### Help to find the joint density function.

Hi, Can someone please help me find the joint density function f(y1,y2) for the given problem. Suppose that Y1 and Y2 are uniformly distributed...

• Replies: 3
• Views: 10,058
04-04-2009, 11:59 PM
56. ### independent and disjoint

If C and D be independent events which are disjoint. What can we said about their probabilities?? i know C, D are independent so P(C n D)=P(C)...

• Replies: 6
• Views: 10,047
11-29-2008, 02:10 PM

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