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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: 31,144
09-30-2005, 09:44 AM
1. ### Expected Value and Fair Value clarification (work already done)

4. In the lottery game FANTASY 5 you have to select 5 numbers from the numbers {1,2,3,... ,38,39} for a jackpot of $40,000. Each ticket costs$1. In...

• Replies: 2
• Views: 2,596
10-08-2013, 10:10 PM
2. ### Difference powerlaw, lognormal and streteched exponential (Weibull) function

I am currently fitting above mentioned functions to my data and I can observe, that both lognormal and Weibull are better fits than powerlaw. In...

• Replies: 2
• Views: 2,959
10-08-2013, 07:40 AM
3. ### Variance and the second moment

Need some help understanding some basic concepts. I understand the first moment of a distribution as being a central point about which the...

• Replies: 2
• Views: 4,313
10-08-2013, 06:11 AM
4. ### How to generate two random vectors correlated to three existing vectors

Let's have three vectors that are given and cannot change (M, N and O). I have to generate two random vectors X and Y. The correlation that has to be...

• Replies: 3
• Views: 2,078
BGM
10-08-2013, 04:13 AM
5. ### Help with cdf

I'm having trouble with grasping cdf's. If I have a cumulative distribution function F(x) = .0 ----- x<-2 ...

• Replies: 5
• Views: 1,782
10-07-2013, 12:12 PM
6. ### Symmetry of Cumulative St. Normal Function

Hi all, I have to show that for the normal distribution F(z)=1-F(-z), starting with the integral: \displaystyle F(z)=\int_{-\infty} ^z...

• Replies: 2
• Views: 1,595
10-07-2013, 07:39 AM
7. ### Gamma Distribution and data fitting

I have a problem with data fitting to gamma distribution. I have rainfall occurrences (calculated using 1st order 2 states Markov Chain analysis) for...

• Replies: 0
• Views: 1,875
10-07-2013, 12:13 AM
8. ### Difference between p(y=0|x=0) and p(x=0,y=0)

Another Trivial question: I have been asked to calculate the joint probability i.e. p(X=0,Y=0) and i have been provided by P(Y=0|X=0), is it the...

• Replies: 1
• Views: 1,712
10-06-2013, 10:18 PM
9. ### Probability question

This is a problem from the book Statistics for Experimenters by Box, Hunter, Box book, page 151. For each sample of 16 boxes of cereal an average...

• Replies: 3
• Views: 1,928
svs
10-06-2013, 08:59 PM
10. ### Mean of Current I with Random variable of R

Hi all, I am new to probability and not so good at it, So please bear with me :) If a voltage e is connected across a resistor whose...

• Replies: 2
• Views: 1,609
10-06-2013, 06:03 AM
11. ### Probabilities associated with simple events

An experiment can result in one of five equally likely simple events, E1, E2..... E5. Events A, B and C are defined as follows. A: E1, E3 ...

• Replies: 0
• Views: 1,719
10-05-2013, 08:50 AM
12. ### Need help with joint distribution problems

1. You need $30,000. Suppose that there is a 20% chance that Bank of America will loan you$30,000, a 30% chance that Wells Fargo will loan you...

• Replies: 2
• Views: 1,438
10-04-2013, 12:13 PM
13. ### Probability (Combination??)

1(a). In a group of 15 students, 9 are boys and 6 are girls. (i). On Sunday, you randomly select 12 students without replacement, what is the...

• Replies: 1
• Views: 1,833
10-03-2013, 05:38 PM
14. ### What is joint probability of these events?

We have two events A and B and three locations X, Y, Z. Each event A and B is carried independently on locations X, Y, Z. The individual probability...

• Replies: 0
• Views: 3,808
10-03-2013, 08:31 AM
15. ### Several True and False Questions!

1. DeMorgan's law states the following: P(A or B)' = P(A' and B') 2. If two events are mutually exclusive then they must be independent. 3. A...

• Replies: 0
• Views: 984
10-02-2013, 11:25 PM
16. ### Probability of hitting a target

I've been trying to work out the probability of hitting a spot in the center of a target and running into some snags. The problem is this: ...

• Replies: 0
• Views: 2,273
10-02-2013, 02:08 PM
17. ### Bounded in Probability proof

Hi all, I could use some help understanding the following proof so please feel free to pitch in! Consider any random variable X with...

• Replies: 5
• Views: 4,933
BGM
10-02-2013, 11:32 AM
18. ### finding probabilty

Consider a country in which 100, 000 people vote in an election. There are only two candidates on the ballot; a Democratic candidate (denoted D) and...

• Replies: 3
• Views: 1,999
10-02-2013, 12:46 AM
19. ### Help with Sample Space question.

Q: There are n marbles in a bag and k(k<n) of these marbles are marked. i) Marbles are drawn from the bag at random (without replacement) until one...

• Replies: 2
• Views: 1,530
10-01-2013, 12:06 PM
20. ### Poisson Distribution Help

Hey, I need some help with the following exercise (big test on Sunday). Q: A lab researching cancer cells found that transformed epithelial...

• Replies: 11
• Views: 2,332
BGM
10-01-2013, 11:33 AM
21. ### Counting Question

Question: If I had X number of train cars and I wanted to know the probability of having Y or more people in a car when I have N total of people. How...

• Replies: 1
• Views: 1,349
BGM
09-30-2013, 06:47 AM
22. ### Need Help

If anyone can take a look at these two problems and see my answers and let me know if I did it correct or am doing it wrong it would be greatly...

• Replies: 6
• Views: 3,153
09-29-2013, 07:27 PM
23. ### this is tricky, have to solve it. come on everyone lets think and try fr possible sol

1. An experiment is conducted repeatedly. At each trial the outcome is either failure or success. The outcome of each trial is independent of all...

• Replies: 1
• Views: 1,802
09-29-2013, 05:49 PM
24. ### binomial distribution help / confirmation

Q: A manufacturer produces 1000 computer chips for a mission-critical application. Each chip costs $100 to manufacture and sells for$2000, but has...

• Replies: 1
• Views: 3,247
09-29-2013, 05:01 PM
25. ### Probability Question from Frederick Mosteller, #7

Hey all, I'm trying to improve my probability skills so hopefully the questions I'm asking aren't too amateur-ish. The following is a question...

• Replies: 1
• Views: 2,094
09-27-2013, 01:01 PM
26. ### HELP! probability that a 7 digit number is divisible by 7?

The seven digits {1; 2; 3; 4; 5; 6; 7} are written down in a random order. What is the chance that the resulting number is divisible by 7? For...

• Replies: 8
• Views: 3,494
09-26-2013, 09:42 PM
27. ### Occupany problem

This is a homework problem that deals with occupancy. Q: consider r indistinguishable balls and n cells where n > r. The r balls are placed at...

• Replies: 6
• Views: 2,791
09-25-2013, 06:47 PM
28. ### Multiple comparisons in SEM

Hello, I am using the Multiple Group Analysis function in AMOS to compare three groups. I am using pairwise comparisons to compare group 1 with...

• Replies: 0
• Views: 1,334
09-24-2013, 10:30 AM
29. ### no clue how to do this question

"The probability that any given person has a certain gene is 0.8 percent. Among people who have this gene, 80% test positively for it. Among people...

• Replies: 4
• Views: 1,848
09-23-2013, 04:51 PM
30. ### Joint marginal conditional probabilities HELP please ;)

An organization was surveyed with regard to the number of children each member had. The gender of the parent was also considered. The results...

• Replies: 2
• Views: 2,686
09-22-2013, 05:55 PM
31. ### Probabilities from Distribution Functions

Buses arrive at ﬁfteen minute intervals starting at noon. Anne arrives at the bus stop X minutes after noon, where X is a random variable with...

• Replies: 1
• Views: 2,664
09-22-2013, 05:06 PM
32. ### Conditional probability problem

Hey all, I hope you can help me with this problem. Say that tomorrow I can go to Berlim with a probability of 20%, Madrid with a probability of...

• Replies: 1
• Views: 1,454
09-22-2013, 02:12 PM
33. ### Prob distribution

The roulette wheel has 38 “pockets”. The “pockets” are numbered 1, 2, …, 36; 0 and 00. Half of the “pockets” 1, 2, …, 36 are coloured red, the...

• Replies: 8
• Views: 1,889
09-22-2013, 07:02 AM
34. ### probability

A congested computer network has a 0.002 probability of losinga data packet and packet losses are independent events. Alost packet must be resent....

• Replies: 1
• Views: 5,014
BGM
09-22-2013, 04:30 AM
35. ### Probability Noob

Hey guys, Im a noob im taking Prob & Stats for Eng. Im only familiar with probability of getting a 4 by rolling a die. Anyway I just wanted to run...

• Replies: 0
• Views: 4,517
09-21-2013, 09:51 PM
36. ### Generalizability of results / External validity

Hi everyone, Employment of probability sampling to draw a sample from the population in a quantitative study (cross-sectional design, data...

• Replies: 5
• Views: 3,625
09-19-2013, 11:59 AM
37. ### Tricky problem about 9 houses

Ace Home Inspectors inspect nine houses each business day. Because AHI has been keeping records for several years they know that the probability of...

• Replies: 0
• Views: 1,399
09-18-2013, 05:14 PM
38. ### Normal Distribution of a chocolate bar

Hey all, I was hoping you can help me out with a question I have trouble translating into math. A factory manufactures chocolate bars with a...

• Replies: 0
• Views: 3,422
09-18-2013, 08:14 AM
39. ### Percentage/zscore

What percentage of drivers drive over 72 mph? I know I have to convert 72 into a Z-score. Im not sure if thats the answer or more to it?

• Replies: 1
• Views: 1,597
09-17-2013, 10:54 AM
40. ### wishart distribution and correlation matrix???

hey there everyone! just a quick question.... you see how the sampling distribution of the covariance matrix follows a wishart distribution (for...

• Replies: 7
• Views: 9,231
Lep
09-16-2013, 03:01 AM
41. ### Came across a very difficult problem...

I really thought hard over this problem for about a hour or two. Here's the problem: A coin has P(head) = p. Keep tossing until you finish a run...

• Replies: 4
• Views: 1,954
09-12-2013, 02:06 PM
42. ### Probability(x<X)

If I have the size of two areas and then the size of the intersection. How may I work out the probability of if I changed an area, the new...

• Replies: 0
• Views: 1,564
09-09-2013, 04:58 AM
43. ### Mean of discrete distributions

Hi All, Need your help on understanding the following. Suppose we have a conditional probability distribution P(C|A,B) over...

• Replies: 4
• Views: 1,991
09-08-2013, 01:32 PM
44. ### Joint Probability problem

Hi again! Have a bit of a problem with this question and would gratefully appreciate some help. There are 4 cards in a game, numbered 1 to 4. A...

• Replies: 3
• Views: 1,938
09-07-2013, 12:44 PM
45. ### College Smokers

This is a proportion of a sampling distribution from what I can tell: I have thought and thought on how to finish this problem. I have read my...

• Replies: 2
• Views: 2,247
09-07-2013, 02:05 AM
46. ### How to use Weibull statistics?

My problem is the following. I have the results of mechanical (tensile) tests performed at different temperatures. I found that below certain...

• Replies: 1
• Views: 1,342
09-06-2013, 10:29 AM
47. ### Area Probability comparison

It's been a while since I have studied statistics, but it seems I need it for my work. I have found and area of intersection between two others...

• Replies: 2
• Views: 1,551
09-06-2013, 04:49 AM
48. ### Small combinatorics question

Hey all! I was hoping you could help me get a 'second opinion' to a problem I ran into. It's most likely one of the most basic combinatorics question...

• Replies: 1
• Views: 1,214
09-04-2013, 10:40 AM
49. ### Tricky problem solution

Hi, A soccer team plays matches. -- If in a previous match it won, it has a 0.6 chance to win in the next match (if it failed, the chances to...

• Replies: 4
• Views: 2,192
09-04-2013, 12:57 AM
50. ### Birthday problem using Bernoulli trails

I came up with this problem: What is the approximate probability that no two people in a group of seven have the same birthday? So, I set up...

• Replies: 5
• Views: 3,104
09-02-2013, 03:36 PM
51. ### Time scaling a geometric random variable

Hello, When one performs bernoulli trials at discrete times t = 1, 2, 3, ....., with the probability of a success at an arbitrary trial given by...

• Replies: 18
• Views: 4,259
09-01-2013, 03:44 PM
52. ### cumulants

I don't know much about cumulants. What I know is that they can be generated by using the cumulant generating function g(t) = \log(E). I'm studying...

• Replies: 1
• Views: 2,164
BGM
08-29-2013, 12:54 AM
53. ### Calculating Hazard Ratios

Hi there, I would like to calculate the hazard ratio (or deviation from the mean) for an 'event' My data has the dates of 'events' and I would...

• Replies: 4
• Views: 8,784
MrT
08-28-2013, 09:12 AM
54. ### Conditional probability problem

One in five of Cadbury's specially marked chocolate bars (Promotion Products) will be packaged in a wrapper that entitles the holder to an instant...

• Replies: 3
• Views: 2,226
08-28-2013, 01:13 AM
55. ### Balls in a jar

I wonder if my approach to this is correct- Say I have a jar with 10 balls, 9 of which are green and 1 that is red. I start taking out a ball at a...

• Replies: 12
• Views: 3,225
08-27-2013, 11:14 AM
56. ### Proving the equality of two expressions

• Replies: 8
• Views: 2,152
08-27-2013, 11:06 AM
57. ### A little help with what seems to be conditional probability

Hey guys, I want to make sure that I'm working this question correctly. Here goes: A jar has 5 white balls. A ball is taken out randomly - if it's...

• Replies: 3
• Views: 1,982
08-26-2013, 04:56 PM
58. ### Weibull distribution for data with zero's

Hi, Can any one tell me how to fit some data with zero's to a weibull fit using Matlab. I tried using Maximum Likelihood Estimator and wbfit....

• Replies: 0
• Views: 1,595
08-26-2013, 11:18 AM

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