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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. ### φ Distribution Table

Hi, I'm currently looking for the φ distribution table, to calcuate marginal effects in a probit model. Unfortunatly there isn't one in my...

• Replies: 0
• Views: 188,791
04-15-2011, 05:59 AM
2. ### Express E[X-μ]^4 in terms of....

X is a random variable with moments E, E, E. Suppose var(X)= σ^2, skewness is given as S=/(σ^3). Express the right side of the following as in...

• Replies: 0
• Views: 132,829
10-16-2011, 10:52 PM
3. ### π-system and monotone class

Assume P is a π-system (that is, P is closed under finite intersections) and M is monotone class (that is M is a non-empty collection of subsets of Ω...

• Replies: 3
• Views: 131,886
BGM
12-17-2011, 10:54 AM
4. ### Μarginal Distributions of f(x,y)

f(x,y) = e^(-x), 0<=x<inf, 0<=y<=1 To find the marginal PDFs here is what I did so far: Marginal Distribution of x: f(x) = integral...

• Replies: 2
• Views: 123,180
10-16-2011, 12:42 PM
5. ### calculation of distance using Kullback–Leibler divergence

Hi, Basically I'm from biology back ground. So it may be a basic question for you. I have two plots for example plot1: X - axis values: ...

• Replies: 2
• Views: 121,521
03-03-2011, 09:39 AM
6. ### Significance Test: Ho & Ha

Me again :) This is a long assingment I'm working on, and I have another question that I'm doubting my answer on.... This is the question: Q: ...

• Replies: 1
• Views: 79,427
11-13-2005, 09:40 AM
7. ### Finding Mean and Variance for X^2 Given Mean and Variance for X

I am working on a question that has me stumped. X1, X2, ... Xn are normally distributed and independent. Each has a mean of 0 and variance sigma^2....

• Replies: 4
• Views: 72,238
11-08-2010, 06:47 PM
8. ### Var(X+Y+Z)

What is the formula for the variance of 3 dependent variables? For 2 dependent variables, the formula is Var(X)+Var(Y)+2*Cov(X,Y) What is...

• Replies: 6
• Views: 67,835
02-09-2015, 02:15 AM
9. ### Help! I’m baffled with a probability problem…..

Hi, Newby here. I am hoping someone on here can assist with a probability question that’s troubling me. I have three ‘events’, in each event...

• Replies: 4
• Views: 65,045
01-09-2012, 11:39 AM
10. ### Help about Isserlis’ theorem

The Isserlis theorem states that if is a zero mean multivariate normal random vector, then : E = EE + EE + EE Now, in the case x,y,z,t are...

• Replies: 0
• Views: 63,240
01-30-2012, 12:38 PM
11. ### Probability Problem

Pls help...........:wave: My problem exercise goes like this - An employee of the records office at a certain school currently has 10 forms on...

• Replies: 74
• Views: 62,368
leo
06-04-2008, 07:00 PM
12. ### probability with mean and standard deviation

The local hardware store sells screws in 1lb bags. Because the screws aren't identical, the number of screws per bag, although distributed...

• Replies: 4
• Views: 61,282
03-06-2012, 05:20 PM
13. ### α = 0.05 vs p-value?

So I've got a couple questions on my stats homework as follows: E. Canis infection is a tick-bone disease of dogs that is sometimes contracted by...

• Replies: 4
• Views: 51,942
09-30-2012, 04:51 AM
14. ### Binomial Probabilities

These kinds of questions can be answered using the binomial probability distribution: 1. If I flip a coin 20 times, what is the probability of...

• Replies: 0
• Views: 48,997
11-01-2005, 02:50 PM
15. ### Calculating z value/mean and standard deviation

Hi...have completed my assignment (and have come a long way with some helpful tips on this forum) but am stuck on one problem: In grading apples...

• Replies: 11
• Views: 42,607
01-07-2006, 10:22 PM
16. ### E[MSE] simple linear regression

Hi All- I am trying to figure out how to prove that MSE = SSE/n-2 is an unbiased estimator of sigma^2 in simple linear regression. I have that...

• Replies: 14
• Views: 41,635
02-02-2013, 03:44 AM
17. ### Doesn't "At least" mean greater than

Thank you for taking the time to read my question :) I was given a question that reads: We would like to test whether the percentage of students...

• Replies: 7
• Views: 36,549
09-27-2010, 10:35 AM
18. ### Standard Deviation from Percentiles and Mean

Hello to all and thank you in advance for the help with this. I am working with a lognormal distribution and am given Percentiles - P10, P50, P90,...

• Replies: 7
• Views: 36,327
12-23-2010, 02:14 PM
19. ### need assistance

I am taking a course in safety and now have one class left, but ran into a big problem. This class has statistics and I don't have a clue. The text...

• Replies: 5
• Views: 36,037
03-05-2006, 06:23 PM
20. ### P-value from test statistic

I'm given a test-statistic of 2.4 in one of those H0 type problem with a 0.05 significance level. In the z-table, if you look up 2.4, it says 0.0082....

• Replies: 8
• Views: 34,885
01-01-2015, 10:33 PM
21. ### Normal Distribution times constant

I can't seem to find anything about this on the web. If I have a random variable distributed Normally: x ~ Normal(mean,variance) is the...

• Replies: 4
• Views: 33,742
02-18-2015, 09:45 PM
22. ### M.g.f for Poisson distribution

Hello, I am having trouble understanding the maths between E(e^{tx}) where I get a summation from 0 to \infty and the m.g.f for Poisson...

• Replies: 2
• Views: 33,554
01-07-2011, 01:55 PM
23. ### Conditional Probability - Exam

Someone can help me please, I need to understand them for my exam on Monday in next week. Today is Saturday.....Thanks a lot..... USING AND...

• Replies: 2
• Views: 29,949
07-13-2016, 01:00 AM
24. ### The Probability of a Flush

Hiya :) Im back for some more assistance.... Q: THE PROBABILITY OF A FLUSH A poker player holds a flush when all 5 cards in the hand belong to...

• Replies: 1
• Views: 29,334
11-14-2005, 09:45 AM
25. ### show P(N>n)=P(X_(n:n)−X_(1:n)<α)

suppose X1,X2,… is sequence of independent random variables of U(0,1) if N=min{n>0:X_(n:n)−X_(1:n)>α,0<α<1} that X_(1:n) is smallest order statistic...

• Replies: 0
• Views: 29,041
08-01-2012, 08:58 AM
26. ### Help with finding indicated probability

I have worked on this problem now for the whole entire day, and still don't understand what I am doing wrong. Can someone help me? The problem...

• Replies: 4
• Views: 29,024
07-13-2008, 06:04 PM
27. ### 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
28. ### MLE of a Gamma Distribution

Hello everyone, I'm having quite some trouble with a question about the maximum likelihood estimator of a gamma distribution. The question is as...

• Replies: 2
• Views: 28,506
11-26-2008, 01:24 PM
29. ### Exponential (θ ) distribution question

Xsub1 and Xsub2 are independent Exponential ( θ ), θ >0, random variables. Let S= Xsub1 +Xsub2 Write the PDF of S stating any standard...

• Replies: 1
• Views: 27,809
BGM
11-08-2012, 11:41 AM
30. ### probability of one random variable being greater than another

I took statistics many moons ago, and remember performing these calculations, but for the life of me I can't remember what this process is called, or...

• Replies: 3
• Views: 27,566
BGM
04-22-2012, 12:38 PM
31. ### mann whitney test or Kolmogorov smirnov test?

I'm working with non parametric methods to compare two samples and detect diferences between them. I used the mann-whitney test and obtained, for all...

• Replies: 23
• Views: 27,040
05-09-2010, 02:28 PM
32. ### Geometric Distribution

A geometric Distribution is a discrete probability distribution of a random variable x that satisifies: 1. A trial is repeated unitl a success...

• Replies: 0
• Views: 26,778
09-14-2006, 05:48 PM
33. ### Find E(X) and VAR (X)

Question is: There is one error in one of five blocks of program. To find the error, we test three randomly selected blocks. Let X be the number of...

• Replies: 10
• Views: 26,661
04-10-2016, 03:54 AM
34. ### Discrete Probability Distributions - Shoot me now!

I spent three hours at a basketball tournament trying to figure these out. Please help. Using the Poisson Probability Distribution I have the...

• Replies: 2
• Views: 26,511
02-13-2006, 09:58 AM
35. ### Dependent Event Vs Independent Event Vs Mutually Exclusive Events

While reading probability book I come across with above terms. Following questions raised in my mind. 1)Are Dependent events always Mutually...

• Replies: 3
• Views: 25,608
01-15-2013, 10:04 AM
36. ### What is the meaning of kurtosis?

I found in Wikipedia that kurtosis is measurement of peakiness of the famous bell curve. If kurtosis is more than 3, it is kind of peaky, if kurtosis...

• Replies: 10
• Views: 25,206
11-09-2011, 12:39 PM
37. ### Expected Value of Exponential Distribution

I've almost completed this problem, but I'm stuck on the last part. The first two parts that I've already shown are also given: a) For a whole...

• Replies: 1
• Views: 24,962
07-03-2007, 01:24 PM
38. ### probability of consumption

could someone let me know what i'm doing wrong? A study of the amount of time it takes a mechanic to rebuild the transmission for a 1992 Chevrolet...

• Replies: 4
• Views: 24,418
06-13-2007, 11:06 AM
39. ### Z-scores for probability in tails

I haven't done any stats in years and now I am in a course for my grad program and I am so lost. My teacher is very confusing and I am trying my best...

• Replies: 3
• Views: 23,966
10-16-2008, 06:45 AM
40. ### finding value of z0

P(|z| > z0) = 0.10 Find z0. I think the answer is z0 = 1.28, however I'm not sure how to get that. The first time I did it, I got 1.645,...

• Replies: 1
• Views: 23,556
08-04-2008, 11:55 AM
41. ### probability

I just posted another question and figured it out by myself but now i'm really stuck. Any suggestions to help me through it? Any input would be...

• Replies: 3
• Views: 23,462
04-14-2011, 06:19 AM
42. ### Poisson distribution

The Poisson Distribution is often used as a model for the number of events occuring within a specific time period. The Poisson probability mass...

• Replies: 0
• Views: 23,359
11-17-2005, 12:25 PM
43. ### I still need help please

Ok, so I am still working on this freaking problem. Can someone help me please. It states that the scenario is normally distributed with a mean price...

• Replies: 12
• Views: 22,993
12-14-2009, 09:10 PM
44. ### sample percentage contained within symmetric limits

Hi! Thank you in advance for assisting with my question. I am working on a probability question and am able to answer almost all of it except one...

• Replies: 3
• Views: 22,977
09-08-2010, 10:57 AM
45. ### Probability on a Multiple Choice exam

Hello, I am not very good at this type of stuff. I thought up something and I was wondering if someone can look over it and tell me if my...

• Replies: 18
• Views: 22,853
12-25-2011, 07:07 AM
46. ### Joint distribution, find P(X^2 + Y^2 <=1)

I am trying to teach myself (without a tutor) some degree level Statistics. I think I've answered parts a-c of this question, but would like...

• Replies: 6
• Views: 22,571
01-17-2009, 02:42 PM
47. ### conditional binomial is a poisson distribution

Hi, I'm fighting with this problem for a while. There is something important I'm missing So the problem goes like this X~Poisson(lambda) and Y|X=k...

• Replies: 13
• Views: 22,175
10-21-2015, 04:01 PM
48. ### Permutations with Duplicates

I have been trying to find information about calculating permutations that include multiple duplicate items, but have only found programming source...

• Replies: 10
• Views: 22,073
10-30-2006, 03:34 PM
49. ### Can't understand some probability symbols.

For two events, A and B, P(A) =1/2, P(B) =1/3, and P(A �� B) =1/4. Find P(B | A). The symbol where is shows a box here is an upsidedown U. Does...

• Replies: 2
• Views: 21,924
06-17-2007, 01:00 AM
50. ### nonstandard normal distributions

I am working a problem regarding IQ scores and am having trouble with one of the problems. I've got it figured out how to work other problems but...

• Replies: 5
• Views: 21,145
07-01-2008, 10:15 PM
51. ### Combine Normal Distributions

How do you combine multiple normal distributions with different standard deviations and means, to produce one representative normal distribution? ...

• Replies: 12
• Views: 20,763
01-26-2013, 12:51 AM
52. ### Events A and B with complements

Hi all, I will show the quest first and my work after. Given: P(A) = 0.3, P(B) = 0.8, P(AUB) = 0.9 A) Find P(A|B), P(A'nB), P(B'UA') B)...

• Replies: 1
• Views: 20,685
BGM
10-24-2010, 01:39 PM
53. ### Maximum of a set of independent normal random variables

Consider a set of random variables X_1, X_2, X_3, \ldots, X_n with unit varience but different means: \mu_1, \mu_2, \mu_3, \ldots, \mu_n . What...

• Replies: 20
• Views: 20,540
07-12-2010, 03:45 PM
54. ### Uniform Probability Distribution

The driving distance for the top 100 golfers on the PGA tour is between 284.7and 310.6 yards (Golfweek, March 29, 2003). Assume that the driving...

• Replies: 5
• Views: 19,903
BGM
04-11-2011, 01:53 PM
55. ### Sum of Poisson Distribution

Hi everyone. Let X and Y be independent, with X~Poi(lambda) and Y~Poi(mu). Put Z = X + Y as their sum. Find the distribution X | Z = z.

• Replies: 8
• Views: 19,409
02-13-2012, 07:50 PM
56. ### Homework help

Hello. I have a minor set back on my homework. So I have a homework problem which states find the probability of the indicated event if...

• Replies: 5
• Views: 19,355
02-26-2009, 11:15 PM
57. ### Standard Normal Variable Z ... I do not understand

:confused: Hi, This is not a homework question as I have the answer, just trying to figure out the method; I have a "Normal Distribution...

• Replies: 2
• Views: 19,046
04-23-2006, 02:33 PM
58. ### Creating a joint probability table

I need help figuring out how to create this joint probability table 43 million people in the United States go without health insurance. Sample...

• Replies: 3
• Views: 19,027
09-03-2009, 09:58 PM

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