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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: 30,337
09-30-2005, 09:44 AM
1. ### binomial probability question

The probability of having a boy = .51 and the probability of having a girl = .49. Find the largest number, "x," that will make this statement...

• Replies: 6
• Views: 3,589
10-14-2009, 10:18 PM
2. ### Simple probability question. Involves drawing name for gift.

We had a dinner with my family where we draw names to give gift this christmas. The only rule was to not pick our name. We did it a couple of time...

• Replies: 4
• Views: 5,516
10-14-2009, 10:08 PM
3. ### Help!!! Normal distribution probability problem..

I don't know if anyone asked similar question before, but the problem asks: The physical ﬁtness of a patient is often measured by the patient’s...

• Replies: 4
• Views: 5,433
10-14-2009, 12:47 PM
4. ### combinations and permutations

hi all, can you all help me wif this question? 1. an art collector, who owns 10 paintings, is preparing her will. how many different ways can...

• Replies: 3
• Views: 3,358
10-13-2009, 12:28 PM
5. ### 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: 6,680
10-13-2009, 11:30 AM
6. ### 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: 6,549
10-12-2009, 01:59 PM
7. ### probability problem

Hi, i'm currently taking intro stats in college and I'm having trouble with probability questions. Here's one of the questions I'm working on: ...

• Replies: 4
• Views: 2,401
10-12-2009, 10:56 AM
8. ### another problem :(

Below are the distributions of blood types in the US and China: Blood type A B AB O US probability .1 .2 .3 .4 China prob. .2 .2 .2 .4 Choose an...

• Replies: 1
• Views: 1,987
10-12-2009, 03:55 AM
9. ### 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: 10,835
10-11-2009, 07:28 PM
10. ### Two Random Variables

Hi, I got a very easy multiple question, I think that the correct answer is missing, please verify... Two independent random variables are...

• Replies: 1
• Views: 2,690
10-11-2009, 10:30 AM
11. ### Determinant of the variance-covariance matrix

Let ∑ be the variance-covariance matrix of a random vector X. The first component of X is X1, and the second component of X is X2. Then det(∑)=0...

• Replies: 0
• Views: 4,407
10-10-2009, 06:15 PM
12. ### Cauchy-Schwarz inequality: cov(X,Y)]^2 ≤ var(X) var(Y)

Suppose that X andy Y are (scalar) random variables. Show that ^2 ≤ var(X) var(Y). (Cauchy-Schwarz inequality) Sow that equality holds if and...

• Replies: 0
• Views: 17,458
10-10-2009, 06:03 PM
13. ### simple probability question

Hello, I need a confirmation to the answer of this question please: It is known that the value of stock A increase in 50% of the days, and...

• Replies: 1
• Views: 3,499
BGM
10-10-2009, 12:03 PM
14. ### Necessary to check normality of definitively non-normal data sets?

hi, i'm working with data sets that are not normally distrubuted, and do not respond with normality to transformations (log, sqrt, z-score). they...

• Replies: 0
• Views: 2,336
10-08-2009, 12:33 PM

I found there is a term of "negative probability" in WikiPedia. Here is the link: http://en.wikipedia.org/wiki/Negative_probability I would...

• Replies: 1
• Views: 2,277
10-07-2009, 06:49 PM
16. ### probability problem

Hi have two probability question I am really struggling to get my head around,would really appreciate some guidance. 1.Drilling of a 100m long...

• Replies: 1
• Views: 2,579
10-07-2009, 06:14 PM
17. ### Binomial Probability Distributions

I am having alot of difficulty in my bio-statistics class can anyone help with these 2 questions? Create pmf and histogram before answering these...

• Replies: 1
• Views: 4,706
BGM
10-06-2009, 01:08 PM
18. ### Multinomial Distribution Question

Demonstrate that the multinomial probability mass function sums to 1 for all possible values of y. Demonstrate that the expected value of Y_i =...

• Replies: 1
• Views: 5,028
BGM
10-06-2009, 02:29 AM
19. ### Density function?

Please can you help me solve this the pdf of continues r.v. X where f(x) {(2x 0≤x≤1 0 elsewhere} 1)...

• Replies: 4
• Views: 3,188
10-05-2009, 04:09 PM
20. ### Joint density

Am a software engineer, and not know much about statsitics but have to explain my younger brother, please help me with this, thanks X1 and X2 have...

• Replies: 2
• Views: 3,674
10-05-2009, 02:59 AM
21. ### Simple Probability Question... That I Don't Understand

I am attempting to do some online homework but I'm stuck on the very first question. The first bit wasn't too hard to figure out (I merely multiplied...

• Replies: 4
• Views: 7,028
10-04-2009, 08:48 PM
22. ### Biased Coin and Conditional Probability

Here's another question that I'm trying to work the kinks out of. Consider a biased coin with the probability of getting heads being p. The coin...

• Replies: 1
• Views: 8,569
10-04-2009, 06:53 PM
23. ### Plz help on this question?

My younger brother asked me and am stuck? Question: Find the probability that exactly four observations of a random sample of size 5 from the...

• Replies: 1
• Views: 2,119
BGM
10-04-2009, 04:37 AM
24. ### Permutations and Combinations Help

I've had some trouble with a recent assignment involving combinations and permutations. I've found this to be my weakest area in my statistics...

• Replies: 2
• Views: 3,355
10-02-2009, 11:02 PM
25. ### prof said wrong but..about the normal probability distribution help!

i read these on the internet but prof said wrong ..can anyone explain me ? 1- It is symmetric about the mean. 2- The total area under the...

• Replies: 1
• Views: 2,087
10-02-2009, 10:53 PM
26. ### is that true?

A process may be out of control even if all the points on the x-bar control chart lie between the UCL and LCL. i that true ? what r u think...

• Replies: 1
• Views: 3,185
10-02-2009, 10:23 AM
27. ### i calculated 22 but i am not sure

This is practice question given by my face to face course assistant... You are in charge of a laboratory which produces high quality, high...

• Replies: 0
• Views: 1,812
10-02-2009, 02:03 AM
28. ### hello

i am study in England. Sometimes i have terrible in statistic.. I have some question.I can say its not my homework..Just for practise just in case:)...

• Replies: 0
• Views: 1,458
10-02-2009, 01:57 AM
29. ### Basic probability

Lets say that I have a population of 2^24 individuals. Each individual, including myself and friends has assigned an individual number. One of them...

• Replies: 0
• Views: 1,949
10-01-2009, 03:42 AM
30. ### Finding mean E[X] using permutations, combinations??

A permutation of the numbers 1, ... 12 is drawn at random, and written on a sheet of paper. For example, 9, 2; 5, 1, 8, 12, 10, 3, 6, 11, 4, 7....

• Replies: 1
• Views: 3,075
09-29-2009, 10:13 PM
31. ### Determining a prob mass function? E[X] and Var[X] help please?

There are 10 chips in a bag: 4 have the number 1 written on them, 2 the number 2, and 4 the number 3. Suppose each chip is drawn with the same...

• Replies: 1
• Views: 2,849
09-29-2009, 10:03 PM
32. ### probability question...

A study revealed that 8% of all ENT bacteria isolated in hospitals nationwide were resistant to vancomycin antibiotic. Consider a random sample of 3...

• Replies: 1
• Views: 2,549
BGM
09-29-2009, 03:48 PM
33. ### 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: 7,411
09-29-2009, 04:01 AM
34. ### Question trouble...

Working on this for a class and wondering if I did this correctly. If anyone could help that would be great. Thanks in advance! 60% of the...

• Replies: 2
• Views: 2,431
09-28-2009, 10:50 PM
35. ### conditional expected value #2

I have two possibilities; X1 and X2. I set up a table: X2: 2: 0: -2 : X1: 0 : 0.1 0.2 0.1 -2: 0.0 0.3 0.3 Then I found: Px1(0)...

• Replies: 4
• Views: 2,974
BGM
09-27-2009, 10:57 AM
36. ### Help, suspiciously common birthdate

I have a database with 41469 medical practice patients. The patients have 22499 different (unique) dates of birth. Sorting by occurrence produces...

• Replies: 4
• Views: 2,568
09-27-2009, 02:23 AM
37. ### Probability in the Design of Social Games

Hey all, I have a math major and in my free time I design online social games. Frequently in these games, players are divided into groups and often I...

• Replies: 4
• Views: 3,123
BGM
09-27-2009, 01:04 AM
38. ### probability problem

I have a probability problem that is confusing me i think over a fine point taht i'm not getting. Here is the problem: a pizza with 8 slices,...

• Replies: 4
• Views: 2,349
BGM
09-27-2009, 12:47 AM
39. ### stuck on a probability problem

THe question is according to the January theory if the stock market is up in Jan. it will be up all year, if its down it will be down all year....

• Replies: 0
• Views: 2,442
09-26-2009, 05:46 PM
40. ### Conditional expected value

I have two possibilities; X1 and X2. The question is: If you know that X1 gives you 0 then what does X2 give you? I set up a table: X2: 2 0 ...

• Replies: 3
• Views: 2,495
09-26-2009, 05:58 AM
41. ### Help!

At a particular location a postal worker clears a letterbox each day. He kept a week’s record of the number of letters cleared. The data are as...

• Replies: 1
• Views: 1,866
09-24-2009, 10:02 PM
42. ### Normal Distribution and Z-Score Help

I am working on a problem and I am having problems with the z-score I calculate. The problem is: A baseball player's average distance is 180...

• Replies: 4
• Views: 4,032
09-22-2009, 02:26 PM
43. ### Probability problem - some help please

The problem reads: Venture capital gave a boost to available funds to companies in the past recent years. According to economic stats, 2,000...

• Replies: 1
• Views: 2,075
09-21-2009, 11:28 AM

A game is played with 2 fair dice. You roll the 1st die and note its score. You will then roll the 2nd die. The game ends if the score on this die is...

• Replies: 3
• Views: 1,863
BGM
09-21-2009, 06:56 AM
45. ### Birthday Problem

Can anyone help me with these questions? I am new in probability and i even don't know where to start..:( (1)What is the minimum number of people...

• Replies: 5
• Views: 3,779
09-20-2009, 04:57 PM
46. ### I'm a pure mathematician. HELP!

Hi, As the title says I'm a pure mathematician. Sorry for the non specific title of the thread, I don't know what the following problem should be...

• Replies: 11
• Views: 3,777
BGM
09-18-2009, 12:30 PM
47. ### Conditional Probability

nvm figured it out!!! sorry!!

• Replies: 0
• Views: 1,755
09-18-2009, 03:20 AM
48. ### What is the probability for this case?

Please help me to understand the following statement that I got it in a research on the piecewise regression analysis. Since I am a medical doctor...

• Replies: 3
• Views: 3,804
09-17-2009, 10:36 PM
49. ### help with contingency table

hi all, i was looking for a little help with a contigency table. the problem states, according to a nutrition table, four products have 35%, 25%,...

• Replies: 0
• Views: 2,667
09-16-2009, 03:41 PM
50. ### Mainly interested in knowing if a solution is even possible.

P(A U B) = .7 P(A U compliment of B) = .9 Find P(A) I've racked my brain and cannot come up with an answer. This is all I've...

• Replies: 1
• Views: 2,162
09-16-2009, 09:01 AM
51. ### Lottery Probabilities

I'm no statistician but hope for some help from the experts. The UK national lottery has been drawn roughly 1500 times since 1994. The frequencies...

• Replies: 2
• Views: 2,985
09-15-2009, 09:08 PM
52. ### "with and without replacement" question

hi, thanks for taking a look. im stumbling on trying to understand one question. the problem is: a box of nine gloves contains two left handed...

• Replies: 1
• Views: 5,683
BGM
09-15-2009, 12:39 PM
53. ### probability of payouts

Hi and thanks for looking at this. We have a client who is donating 10% of pet ecommerce profits to shelters. We are building an online slot...

• Replies: 0
• Views: 2,238
09-15-2009, 11:13 AM
54. ### Discrete and Random Variables

I'm not sure how to setup this problem. It says: To perform certain type of blood analysis, lab technicians must perform two procedures. The...

• Replies: 1
• Views: 9,758
09-14-2009, 08:30 AM
55. ### Probability Homework

I have a probability question that I have no idea where to start. It is probably simple but I don't have any idea where to start. I was thinking it...

• Replies: 0
• Views: 2,812
cjb
09-13-2009, 10:52 PM
56. ### Probability question. Need help!

Suppose I have faith in my local weather reporter who says that the chance of rain tomorrow is 80 percent. Moreover, my friend, the seasoned sailor,...

• Replies: 0
• Views: 2,201
09-13-2009, 04:49 PM
57. ### Mathematical Probability with respect to Frequencies

I am trying to figure out what the chances are of a run of 13 blacks in a row happening over the course of 80,000 spins of a roulette wheel. I am...

• Replies: 1
• Views: 2,232
09-13-2009, 10:03 AM

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