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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: 30,265
09-30-2005, 09:44 AM
1. ### Likelihood Theory

Hi. I'm working with the exponential density f(x;theta) = theta * exp (-x*theta). I'm asked to verify the Var = -E. I've worked out the right...

• Replies: 3
• Views: 3,447
09-26-2011, 10:25 PM

the annual profit for your organisation last year was $1203, per employee. The average for the sector was$1228 per employee. You need to know if...

• Replies: 0
• Views: 2,494
09-26-2011, 02:35 PM
3. ### Stuck on a (trivial) derivation for mixed effects linear models...

i know this is horribly basic, but for some reason i'm not on top of my game now and cant work something very easy out. the general...

• Replies: 4
• Views: 2,726
09-26-2011, 09:44 AM
4. ### Help with understanding this expected value proof

can someone please explain this. My instructor did this but I don't really understand how. I have E(Y*E(YlX)) from theorem of total...

• Replies: 3
• Views: 3,397
BGM
09-26-2011, 04:06 AM
5. ### Hypergeometric distribution

Sorry I could not delete it

• Replies: 1
• Views: 1,518
BGM
09-25-2011, 08:16 AM
6. ### Darts probabilty

when we throw a dart at a target, we have a probability of 1/4 of hitting the target . what is the probability of obtaining at least one hit if three...

• Replies: 1
• Views: 1,622
BGM
09-25-2011, 07:49 AM
7. ### Distribution Doubts !

For this question, Find the probability that the 5th toss is a head. The answer is 1/2 because it's independent. Previous 4 tosses will not...

• Replies: 1
• Views: 1,714
BGM
09-24-2011, 01:04 PM

Find the probabilities of getting (a) three 3's and then a 4 or 5 in four rolls of a balanced die. P(three 3's) = P(3rd is a three | 2nd is a...

• Replies: 2
• Views: 2,627
09-24-2011, 12:02 PM
9. ### Card Probability Problem

I seem to have a brain cramp and need some help. A card is chosen randomly from a standard deck of 52 cards and replaced. On average, how many...

• Replies: 2
• Views: 2,136
09-23-2011, 05:04 PM
10. ### another stats

an experiment consists of choosing a point (x,y) at random from the interior of the circle disk x^2+y^2= 4 a/ find P(X>or = 1/2) b/ find the...

• Replies: 0
• Views: 1,693
09-22-2011, 04:33 PM
11. ### need help with stats

hurricanes hit florida independently of each other, at an average rate of once every four years. what is the probability that florida will be hit by...

• Replies: 1
• Views: 1,895
BGM
09-22-2011, 01:36 PM
12. ### stats uniform distribution

suppose the random variable Q is uniformly distributed on the interval . find the probability that the roots of the equation 4t^2 +...

• Replies: 1
• Views: 3,666
BGM
09-22-2011, 01:23 PM
13. ### Different between "X % more likely" vs. "X times more likely"

I often see something like "smokers are 10% more likely to get cancer than non-smokers." Is this equivalent to saying smokers are "10 times more...

• Replies: 0
• Views: 28,773
09-21-2011, 10:25 PM
14. ### need help to calculate variance of sales

Hi, I'm trying to calculate numerical value of the variance of sales, and the probability of a sale greater than 6300 cans. but it seems wrong...

• Replies: 14
• Views: 6,763
09-21-2011, 07:18 PM
15. ### Pattern Recognition (Bayesian Statistics) :D Perhaps someone could help!

:D Greetings everyone! The question is: A) Its on bayesian statistics, specifically error. So the question first states that Total error = the...

• Replies: 0
• Views: 2,180
09-21-2011, 12:24 PM

1. Say we are interested in the effect of a new medication that may help people with an illness. 40% of all people in our population of interest have...

• Replies: 0
• Views: 2,771
09-21-2011, 10:39 AM
17. ### expected standard deviation and confidence interval

Hi, I have a problem with scoring an ipsative questionnaire. In this questionnaire people get 7 different statements in which they divide balls...

• Replies: 0
• Views: 1,930
09-21-2011, 04:48 AM
18. ### Probability and percentiles

An airline has found from past experience that the weight of checked-in baggage items is Normally distributed with mean 13 kg and standard deviation...

• Replies: 0
• Views: 3,362
09-20-2011, 11:50 PM

:shakehead The class had calculated that 80% of Statistics and Modelling lessons, are interrupted by one or more notices. Find a) the average...

• Replies: 4
• Views: 3,079
09-20-2011, 02:19 AM
20. ### Gamma Difference Distribution

What is the distribution of the difference of two gamma distributions with same scale parameter, and shape parameter of the first one is k(1+e), e ->...

• Replies: 1
• Views: 4,459
BGM
09-19-2011, 10:43 AM
21. ### Neat Problem w/Time Dependence (Bayesian?)

Assume a finite set of N probability distributions with shapes that change in time. The shapes change in a known fashion with time, and are...

• Replies: 3
• Views: 3,021
09-17-2011, 10:01 AM
22. ### I need Probability help

hey folks! I've been given two probability questions for my home assignment. I've been trying to solve these problems but having difficulty...can...

• Replies: 4
• Views: 3,848
09-17-2011, 04:40 AM
23. ### Need some help with basic probability!

Hey, I need some help with two probability question, and I would really appriciate all the help I can get! QUESTION 1: (a) A quality inspector...

• Replies: 5
• Views: 4,742
09-16-2011, 03:43 AM
24. ### Why can't t/(1-t) be a moment generating function for a R.V?

Hi there, having a bit of trouble with this one: Explain/show why there can be no random variable for which Mx(t) (moment generating function) = t...

• Replies: 11
• Views: 9,645
BGM
09-15-2011, 03:08 AM
25. ### joint probability questions help?

You were given the following joint probability function for Y1 = { 0, if the child survived, 1, if not, and Y2 = { 0 if no belt used, 1 if adult...

• Replies: 0
• Views: 3,304
09-14-2011, 07:14 PM
26. ### Gambling system significance

I have a gambling system that I've been using on NFL games since November of 2009. So far there have been 128 plays and the record is 80 wins and 48...

• Replies: 5
• Views: 3,756
09-14-2011, 03:42 PM
27. ### Proabability

Hi I've Some Question like this, Employees of a local university have been classified according to gender and job type. If an employee is...

• Replies: 0
• Views: 3,386
09-14-2011, 01:51 PM
28. ### Probabilities: "Drunk is 10 steps away form falling in the dock"

A drunk is 10 steps away from falling in the dock. Every step he takes is either directly towards or away from the dock and he is equally likely to...

• Replies: 4
• Views: 3,215
09-14-2011, 12:28 PM
29. ### really urgent probability problem - is it bayesian?

Hi, I have an urgent problem but I'm a little lost. Is this probability question referring to the use of Bayes' theorem? Firstly, I don't...

• Replies: 4
• Views: 2,818
BGM
09-14-2011, 08:48 AM
30. ### Probability Question

I have been trying to work though this problem and have gotten stuck; I am trying to set up a table to help me calculate the probabilities...

• Replies: 1
• Views: 6,146
09-12-2011, 03:27 PM
31. ### Drawing more than 1 marble

Hi, My answer doesnt tally with the answer provided, can someone please have a look and figure out where I am mistaken? Thank u so much If four...

• Replies: 2
• Views: 2,419
BGM
09-12-2011, 01:14 PM
32. ### Solve this??

There are w cakes and n people. The cakes are distributed to people randomly. Find the expected number of cakes a 'i' person can receive. The...

• Replies: 1
• Views: 1,863
09-12-2011, 07:10 AM
33. ### Standard deviation and mean, find probabilities.

Hi guys, the question is this, (it's a first year stats course online quiz question) Tourism Queensland monitored the duration of calls to...

• Replies: 1
• Views: 3,918
09-11-2011, 08:11 AM
34. ### Bayesian inference - or maybe i'm doing that wrong?

So first of all - hello! Now, my problem: So I started baye's theorem, and tutor said, that mostly i will need that formula: In denominator...

• Replies: 3
• Views: 2,498
09-10-2011, 10:54 AM
35. ### Dice probability

Hello people, I have a very simple probability question that I need to solve a problem (recreational mathematics). Anyway, I would like to know how...

• Replies: 3
• Views: 2,004
BGM
09-08-2011, 11:52 AM
36. ### Assessing goodness of fit across many variables in R in one session.

Hi all I'm just getting started in R and would like some help with the following problem which could make life easier I hope! I have data set...

• Replies: 5
• Views: 1,957
09-06-2011, 05:54 PM
37. ### I need solution for this problem ASAP. Probability problem with two arrays of holes.

Given two arrays of holes, Each hole can be filled in by a white ball or a black ball. 1. Each array has n holes, and can be filled in by r black...

• Replies: 2
• Views: 2,122
09-06-2011, 07:10 AM
38. ### Basic (or maybe not so) probability problem/experiment/question.

I came upon an interesting probabilistic assertion in a book I'm reading. Here's the quote: "Once in a while we find co-occurrences, and we're...

• Replies: 6
• Views: 2,737
BGM
09-06-2011, 03:20 AM
39. ### Joint Probability

Hi everyone, For any generic continuous joint CDF, what is the probability of Pr(X=z,Y=z) where X and Y are two random variables on the support of...

• Replies: 10
• Views: 3,188
09-05-2011, 12:36 PM
40. ### Bayes Theorem Question for Probability Newbie

Hi, I'm trying to brush on probability for a graduate class. I've been reading about bayes theorem, which my book states as: P(A | B) = P(B |...

• Replies: 2
• Views: 2,480
09-05-2011, 10:42 AM
41. ### Probability question.... refresher

Hey all, I'm trying to remember some basic combination stuff. Here's the question. There are 8 seats in a line. If 4 boys and 4 girls are seated...

• Replies: 2
• Views: 1,953
09-04-2011, 04:43 PM
42. ### What is the chance to have a mutual friend with a random person ?

We have a social network say facebook. We know that it is composed by 500 milion of users. We know that each user have an average of 135 friend. ...

• Replies: 8
• Views: 9,951
09-02-2011, 06:35 PM
43. ### probability question about composing a song

i have 450 numbers and i want to know which group of numbers have more probability lower of the average or higher and why :i dont know statistics...

• Replies: 0
• Views: 1,425
09-01-2011, 01:01 PM
44. ### Comparing Gaussian curves

Hi, I have two points A(30.333,100) and B(30.333151665,80) I need to draw Gaussian for each point separately and need to check their overlap...

• Replies: 7
• Views: 9,140
08-31-2011, 05:35 PM
45. ### Chi-squared and T distribution, just need a check

These problems where review from a prior class, i think they are correct but not positive. Q1. Using the T distribution, find the following and...

• Replies: 1
• Views: 2,025
BGM
08-31-2011, 12:03 PM
46. ### Choice probability

I need to calculate the binary choice probabilty of 2 alternatives i and j- Each of the alternative is charectarised with a part of measurable and...

• Replies: 1
• Views: 2,425
BGM
08-31-2011, 11:59 AM
47. ### Same player winning the jackpot twice

Hi Here in Sweden a scratch card buyer managed to buy two scratch cards with the top prize. The top prize is very rare so this caused some...

• Replies: 5
• Views: 3,011
08-31-2011, 11:18 AM
48. ### product of N normal distributions

We are given N normal functions, with means \mu_i, and variances \sigma_i^2, i in 1...N. I need to find a formula for the product of the N...

• Replies: 2
• Views: 4,986
08-26-2011, 05:06 PM
49. ### expectation of conditional probability

Hi there, I have two questions which I found answers to slightly different version of them in books but not to those that I have in mind so please...

• Replies: 12
• Views: 4,396
BGM
08-25-2011, 02:09 PM
50. ### multivariate mutual information

Hello everyone :wave:, I wonder if the equation concernat multivariate mutual information MI (X, Y, Z) = MI (X, Y) - MI (X, Y | Z) is the same...

• Replies: 1
• Views: 2,599
08-25-2011, 07:01 AM
51. ### Probability a Selection wins the most races

I have 12 races with 6 participants (Sel'n 1 - Sel'n 6) and below is the probablities on how many wins each selection would get... Sel'n 1 Sel'n...

• Replies: 2
• Views: 2,415
08-24-2011, 03:55 PM
52. ### Probability Density function table

given the pdf table for function pxy(x,y) for 2 discrete random variables X and Y which take values 0,1. What do E and Cov(X,Y) equal and what is the...

• Replies: 4
• Views: 4,331
08-24-2011, 09:45 AM
53. ### r-value > Probability

I have two wrestlers who are going to arm-wrestle. I want to try to predict who will win based on their previous fights against other opponents....

• Replies: 14
• Views: 7,035
08-24-2011, 06:14 AM
54. ### Probability Table Question

Hi, I have been working on part (d) of the following question for so many days and I just can't carry on anymore because I'm too confused. ...

• Replies: 0
• Views: 1,714
08-24-2011, 01:12 AM
55. ### showing estimator is the minimum variance estimator for a

Let X_1, X_2,...,X_n be a random sample from a geometric distribution, with probability function given by. ...

• Replies: 3
• Views: 3,072
08-23-2011, 03:17 AM
56. ### another baseball question

Player will bat 4 times in this game. He is expected to get a single .15 of the time he goes to bat for 1 total base, he will get a double .05 a...

• Replies: 0
• Views: 1,902
08-22-2011, 04:27 PM
57. ### Convolution and conditionning: S=X+Y X=two point distribution Y=Normal

Hello, can anyone help to find the conditional distribution of X given S if S=X+Y X is a r.v. {0,1} 0 with probability p and 1 with probability...

• Replies: 1
• Views: 3,032
BGM
08-22-2011, 10:46 AM
58. ### drawing more than one marble at random

Hi, Can you please check my solutions? I guess, I have got them right.Thanks Probability 1) If four marbles are drawn at random from a bag that...

• Replies: 4
• Views: 4,832
08-22-2011, 08:30 AM
59. ### okay need insight on this...

I have attempted to work this out twice use 2 different formulas (1.interval estimation of a population mean (small-sample case) 2. interval...

• Replies: 4
• Views: 3,525
08-22-2011, 06:56 AM

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