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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: 30,232
09-30-2005, 09:44 AM
1. ### Bidding question - (Uniform Probability Distribution)

Suppose you are interested in bidding on a piece of land and we know one other bidder is interested. The seller announced that the highest bid in...

• Replies: 4
• Views: 18,983
02-14-2006, 12:26 PM
2. ### Help with Probability!

Hi. I came across a few questions tht i came across while studyin for a probability chapter. Just a little request, im very new to probability so u...

• Replies: 5
• Views: 18,955
12-09-2010, 10:41 AM
3. ### Crying inside 😖 just can't quite get probability

I'm taking stats online and this unit is on probability. I'm having a terrible time understanding it. The conditional probability rule is where I'm...

• Replies: 0
• Views: 18,768
06-29-2015, 03:03 AM
4. ### how to find probability with percentages?

Say i have 25% of the sodas are pepsi and there are a certain number of those pepsi's with a special code under the cap how could i find the...

• Replies: 4
• Views: 18,619
03-17-2013, 05:19 PM
5. ### difference between binomial exact test and fisher's exact test

Hello all, So I know the general difference between these tests --binomial exact test is used to test for a significant difference between and...

• Replies: 1
• Views: 18,365
01-31-2012, 11:04 AM

This problem is driving me crazy! The length of time to complete a door assembly on an automobile factory assembly line is normally distributed...

• Replies: 7
• Views: 17,700
12-18-2005, 01:56 PM
7. ### 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: 17,451
10-10-2009, 06:03 PM
8. ### Equation for the Standard Normal Curve

Does anybody know what the equation is for the standard normal curve? In my statistics class, we use a chart to find areas under the curve given...

• Replies: 6
• Views: 17,441
04-16-2010, 04:52 PM
9. ### This probability problem is all over the internet...

This seems to be a common statistics homework question, as it is all over the internet. Because of this, I know the answer (0.2904), but that is not...

• Replies: 3
• Views: 17,250
10-28-2009, 05:02 PM
10. ### too many gumballs

i am pulling my hair out over this chapter on probability. First question which formula do I use to determine this answer. A gumball machine...

• Replies: 1
• Views: 17,233
10-07-2005, 02:25 PM
11. ### Immortality & Bayesian Statistics

- I seem to have written an 8 page paper virtually proving -- through Bayesian statistics -- that we are immortal (or something similar). Obviously,...

• Replies: 81
• Views: 16,975
04-06-2015, 05:11 PM
12. ### Confidence Interval for gamma distribution mean

Hello I have a same problem which has been irritating me for so long now. The internet was no help so I post it here. If any of you guys have any...

• Replies: 3
• Views: 16,955
02-27-2013, 04:07 PM
13. ### E(X) < ∞ ? What does it mean?

Let X and Y be random variables, F be a function. I have seen in a variety of contexts that they write "E(X) < ∞". What does it mean? My guess is...

• Replies: 5
• Views: 16,868
07-15-2009, 05:30 PM
14. ### Probability Homework(2)

The deeper i go into the probability chapter, the more confused i get :(, here are sum questions. they might be really easy but i'm not getting them....

• Replies: 9
• Views: 16,840
02-24-2012, 11:19 PM
15. ### probability of failure in a multi-component system

I want to calculate the failure rate of a system that has multiple independent points of failure. If any one of these intermediate points fail then...

• Replies: 2
• Views: 16,585
01-19-2010, 10:09 AM
16. ### Pollutants in auto exhausts.

Hello all - I am in need of some assistance with a probability problem. I am thoroughly confused and I don't know what to do. Any help is...

• Replies: 2
• Views: 16,418
10-25-2009, 11:26 AM
17. ### Confidence Interval and SRS

Another quick question.... Q: Running Red Lights A survey of licensed drivers inquired about running red lights. One question asked "Of...

• Replies: 1
• Views: 16,151
11-14-2005, 09:27 AM
18. ### Characteristic function of the Gamma distribution

I have not been able to find anywhere a rigorous derivation of the characteristic function of the Gamma distribution. Any suggestions?

• Replies: 3
• Views: 16,135
11-18-2011, 03:41 AM
19. ### Product Normal Distribution

Hi, Summing normal distributions is nice and easy, providing another normal distribution. But multiplying gives the Product Normal Distribution....

• Replies: 6
• Views: 15,988
01-20-2012, 12:54 PM
20. ### Combining two different normal distributions.

I have done the following question: In a hospital, 1/3 of the people who use a particular elevator are adults and 2/3 are children. The weight of...

• Replies: 10
• Views: 15,799
11-23-2010, 10:41 PM
21. ### Standard Normal Distribution

Here is a question that I am trying to answer for myself. I think I figured out A alright. Anyway, here it is: In the standard normal...

• Replies: 2
• Views: 15,797
06-15-2008, 09:58 PM
22. ### Independent Event if A is a subset of B ???

I have a questions regarding Conditional Probability. Two events A and B are independent if: P(AnB)=P(A)*P(B) Is this always the case or are...

• Replies: 5
• Views: 15,770
10-23-2011, 04:55 PM
23. ### Births

Assume that male and female births are equally likely and that the birth of any child does not affect the probability of the gender of an other...

• Replies: 1
• Views: 15,766
10-09-2005, 09:22 PM
24. ### Distributive Law P[A u (B n C)]

I am trying to find a synonymous formula formula for: P = P Can anybody help me? I found somewhere that said it was equal to P but I...

• Replies: 4
• Views: 15,724
11-05-2011, 04:07 PM
25. ### Generate Random Correlated Variable

I have established a correlation between independent X and dependent Y. Is there a formula for generating a random Y from a particular X? For...

• Replies: 17
• Views: 15,238
06-29-2012, 09:43 AM
26. ### Poisson Distribution Conditional Probability

Hello, My name is Chris and I would greatly appreciate some help concerning the folowing Probability problem. Suppose that the number of...

• Replies: 4
• Views: 15,190
11-08-2010, 10:53 AM
27. ### Immortality and Conditional Probability

- Hopefully, I won't aggravate readers so much with this approach. - Here, my claim is simply that the likelihood of my current existence is...

• Replies: 71
• Views: 14,521
04-22-2015, 06:50 AM
28. ### show that the sum of e(i) = 0 and the sum of e(i)*Yhat(i) = 0

Consider a usual multiple linear regression model: Y = X β + ε where Y is a (n x 1) response vector, X is a (n x p) matrix with its first column...

• Replies: 16
• Views: 14,506
BGM
11-14-2011, 02:40 AM
29. ### variance of binomial distribution

The variance of a binomial distribution for which n = 100 and p = 0.20 is this is a practice problem for a test im taking next week. But i don't...

• Replies: 1
• Views: 14,493
02-23-2009, 09:46 PM
30. ### E(X) , Cov(aX,bY)

Let X and Y be random variables with the density f(x) such that f(X)=1 for 0<x<1 and f(x)=0 for x<0 and x>1. We have that Var(x) = Var(Y). 1)...

• Replies: 12
• Views: 14,173
04-24-2012, 08:52 PM
31. ### find the expected value of continuous random vaiable

Hi, To find the expected value of a continous random variable I normally integrate the pdf multiplied by the random variable over the range of the...

• Replies: 10
• Views: 14,136
11-20-2009, 07:05 AM
32. ### Can't figure out probability question...

Ok, so I'm completely lost in my Statistics class and I really need help on this problem. I think if I figure this one out, it will help with the...

• Replies: 1
• Views: 14,111
10-20-2009, 10:52 AM
33. ### Show Skewness of a symmetric pdf to be 0

Hi there, I am hoping some of you may be able to help/guide me! I am taking a course in turbulence which has an obvious background in statistical...

• Replies: 1
• Views: 14,093
BGM
01-03-2011, 04:58 PM
34. ### Method of Moments, MLEs, and Standard Errors

Hi, I have a question about standard errors in the context of this problem. Any help would be greatly appreciated: Suppose X is a discrete random...

• Replies: 13
• Views: 13,999
BGM
02-07-2010, 04:13 PM
35. ### technical VS biological replicates (compare means)

Hi, I have conducted an experiment with an assay for 2 biological classes, each consisting of 10 unique members. I did the assay 3 times for a...

• Replies: 4
• Views: 13,992
07-18-2010, 05:49 PM
36. ### Joint PDF problem

Hey folks, I've got a problem with a joint probability density function question. Given f(x, y) = 6(x^2)y for 0 <= x <= y, x + y <= 2 and 0...

• Replies: 21
• Views: 13,904
10-13-2010, 05:20 PM
37. ### Difficult Integral standard normal pdf/cdf

I would like to get an explicit analytical form for the integral (below)...or something close to it with an associated (small) error term. (Note that...

• Replies: 17
• Views: 13,881
BGM
05-31-2010, 09:35 AM
38. ### Minimum of 2 Random Variables question

R(1) and R(2) are 2 independent random variables with same density function f(x) = x*(e^(-.5 * x^2)) for x >= 0. Find the density of Y = min{R(1),...

• Replies: 7
• Views: 13,805
11-05-2010, 11:13 PM
39. ### Sample mean and variance of dependent random variables

The sample mean and variance of independent random variables are mean = E(X) variance = Var(X)/n What if the random variables are dependent? ...

• Replies: 1
• Views: 13,424
07-10-2008, 03:57 AM
40. ### Calculating probability of multiple events

This is my first post so I hope I can get my question across reasonably intelligently. I have calculated the probability of an event occurring for...

• Replies: 3
• Views: 13,415
11-26-2008, 05:24 AM
41. ### Probability Density Function and Cumulative Distribution Function

Hi everybody, If anyone has experience working with probability density functions (pdf), please look these sample problems over and if you could,...

• Replies: 5
• Views: 13,346
09-27-2010, 06:34 AM
42. ### Need lots of help - Binomial Probabilities

I completely confused on this my problem is this: Richard has just been given a 10 question multiple-choice quiz in his history class. Each...

• Replies: 2
• Views: 13,223
11-16-2005, 10:29 PM
43. ### introduction to stochastic process by by Hoel, Port and Stone.

those any one have this text. i have gone through all the questions in chapter 1 except for two prove questions. no 27 and 26 i am lost

• Replies: 6
• Views: 13,100
07-16-2010, 02:05 PM
44. ### probability of liscense plate

What is the probability of getting a license plate that has a repeated letter or digit if you live in a state where the scheme is three letters...

• Replies: 1
• Views: 12,996
10-06-2007, 08:21 AM
45. ### percentile for (1 - cumulative distribution function)

Hi, Before addressing my question, please let me define the context: The percentile is usually defined as the value of a variable BELOW which a...

• Replies: 4
• Views: 12,963
01-04-2011, 10:09 AM
46. ### I need some help, please

Hi, I have found some difficulty in solving this exercise. HINT: Use the fact that T/σ^2~chi-squared (n-1) and the moments of the chi-squared...

• Replies: 28
• Views: 12,890
11-13-2013, 04:10 PM
47. ### Determining Joint PDFs, and Marginal PDFs

Hi All, I'm going through revision questions, and I am stuck on this particular section all with similar questions. If somebody can give me a guide...

• Replies: 13
• Views: 12,868
05-15-2008, 01:04 AM
48. ### Law of Total Expectation

The law of total expectation states that: E(X) = E and E = Eg(X)|Y)] 1) Now, is it correct to say that E(XY)=EXY|Y)] ? I don't think the above...

• Replies: 10
• Views: 12,744
11-18-2009, 02:28 AM
49. ### Maximum likelihood estimator question with discrete uniform distribution

Q. A bag contains sequentially numbered lots (1,2...N). Lots are drawn at random (each lot has the same probability of being drawn). Two lots are...

• Replies: 9
• Views: 12,704
BGM
03-06-2011, 01:15 PM
50. ### Cumulative Beta Distribution Function Help

Hi everyone, I was wondering if someone could help me figure out how this function works. My problem is not that I need homework help, it's that...

• Replies: 13
• Views: 12,608
05-05-2014, 04:07 AM
51. ### Relation between n, p, q, and sigma

I know the value of n and p. I am looking for the standard deviation and mean based on those values. I gather that the forumla for sigma, the...

• Replies: 1
• Views: 12,589
06-07-2010, 04:52 PM
52. ### Cup and ball game: what are the odds of that?

OK we are having an intelectual discussion (no, really) about the change in odds during the classic cup and ball game. To explain: a dealer has...

• Replies: 2
• Views: 12,551
02-22-2010, 08:00 PM
53. ### Hypergeometric Probabilities

These are similar in principle to the binomial distribution, with one major exception - the hypergeometric probability is for situations where you...

• Replies: 0
• Views: 12,545
02-20-2006, 11:59 AM
54. ### Probability of coincidence ?

Probability of coincidence ? (WARNING... resolving this problem may force upon you world fame and extreme wealth) I basically don't know where to...

• Replies: 40
• Views: 12,491
02-27-2014, 09:21 PM
55. ### Odds of birthday on same day

I'm confused about the following... Two people have their birthday on a specific day of the year. Are the odds 1:365 or 1:730 ? :confused: ...

• Replies: 7
• Views: 12,482
02-18-2010, 04:09 PM
56. ### Probability Concepts Homework Help!!

Hi, I have been struggling with this question for the past few days now and still can't seem to figure it out. If anyone can help me and show me...

• Replies: 7
• Views: 12,457
02-24-2010, 12:51 PM
57. ### Is P(A n B) the same as P(B n A)?

As the topic says. If we have two events A and B respectively, is it possible that P(A n B) != P(B n A)? This isn't a homework question but its...

• Replies: 1
• Views: 12,385
10-05-2010, 03:44 PM
58. ### Discrete Probability

Hello all. I recently became a member on this forum. Hope to learn many new things from here and in my statistics course in college. I am still...

• Replies: 1
• Views: 12,324
BGM
02-24-2011, 12:06 AM
59. ### Expected Profit

This question is really confusing me: The annual profit Y(in \$100,000) can be expressed as a continuous function of drug demand x(in 1,000): Y(x)...

• Replies: 6
• Views: 12,254
03-21-2011, 10:53 PM

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