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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: 30,376
09-30-2005, 09:44 AM
1. ### standard deviations in scatter plots

I am working with data that involves blood volumes in the heart according to gestation. I have plotted these values using a twoway scatter graph. I...

• Replies: 1
• Views: 6,717
10-22-2010, 01:16 PM
2. ### converges almost surely

I need to use this lemma for my prove, and I dont know how to prove this lemma. "X_n \rightarrow 0 a.s iff for all \epsilon > 0, P(|X_n| > \epsilon...

• Replies: 0
• Views: 2,720
tup
10-22-2010, 01:08 PM
3. ### converges in prob

Let X_1, X_2, ... be independent with P(X_n = 1) = p_n and P(X_n = 0) = 1- p_n. Show that (i) X_n \rightarrow 0 in probability iff p_n \rightarrow 0,...

• Replies: 2
• Views: 2,184
tup
10-22-2010, 12:39 PM
4. ### Is this possible?

Hi, please help me out with this problem. I want to calculate P(X <= x) = P(sum(1->n)(Z_k) <= x) where sum(1->n)(Z_k) is the sum of Z_k from 1 to...

• Replies: 4
• Views: 2,064
10-22-2010, 08:23 AM
5. ### Random sample probability with no max population size

Hi all, I have no clue what to do with the following question... In a random sample of 20 cassettes, what is the probability that at least two...

• Replies: 1
• Views: 4,838
10-21-2010, 08:55 PM
6. ### cant decide null and alternative

. Last fall, a sample of n= 36 freshmen was selected to participate in a new 4-hour training program designed to improve study skills. To evaluate...

• Replies: 7
• Views: 4,945
10-21-2010, 06:41 AM
7. ### i need help with this question of probability!

I need help with answering this questions. Suppose that the fills in the soda pop bottle are normally distributed with mean 32.2 ounces and st...

• Replies: 1
• Views: 4,995
10-20-2010, 09:16 PM
8. ### Two Probability Questions

1. 50 vaccines are tested on patients to see how well they treat a virus. The results of the tests are recorded in this table. ...

• Replies: 1
• Views: 2,491
10-20-2010, 08:37 PM
9. ### prob. questions

Let we have 3 urns with a white, b black balls in each urn. We choose one ball from urn 1 and transform it to urn 2. Then, choose one ball from urn 2...

• Replies: 5
• Views: 2,947
10-20-2010, 05:01 PM
10. ### Expected Value of the Difference

The heights of all male students in a university have mean 170 cm and standard deviation 10 cm. Two male students are randomly selected. What is...

• Replies: 3
• Views: 8,883
10-20-2010, 03:31 PM
11. ### Confidence Interval homework check if correct

1. 68.6 I did this by solving for x with this equation .004=1.96(.14/sqroot of x) 2.84.72% I found this by finding zscore for 1.43 which was...

• Replies: 5
• Views: 4,491
10-19-2010, 04:56 PM
12. ### Multivariate normal distribution

Hi, I want to calculate expected value of a series. Where X = A + 2B +3C + ..... A = bivariate normal B = trivariate normal C =...

• Replies: 1
• Views: 2,593
10-19-2010, 03:47 PM
13. ### Finding E[X] and Var[X] of exponential distribution

Transistors produced by one machine have a lifetime which is exponentially distributed with mean 100 hours. Those produced by a 2nd machine have an...

• Replies: 7
• Views: 10,239
10-19-2010, 12:23 PM
14. ### Joint probability distribution table

Helllo, I have this problem for an assignment: 1. It is known that box C has 3 blue balls, numbered from 1 to 3, and 2 red balls, numbered from 4...

• Replies: 1
• Views: 8,162
10-18-2010, 05:16 PM
15. ### A little help with distributions

I have been assigned a project that involves statistics and i have no idea about it. I was suppose to capture online game traffi and then using the...

• Replies: 8
• Views: 3,454
10-18-2010, 01:07 PM
16. ### Pricing and probablity problem

Company 'A' sells an item and want to know what is the best price to sell it at. They have done some market research on the customers coming through...

• Replies: 1
• Views: 2,285
BGM
10-18-2010, 12:20 PM
17. ### Probability

I dont know how to express this answer mathematically, please help? A coin is tossed three times. Express the probability that the oucome is: ...

• Replies: 1
• Views: 1,949
10-18-2010, 07:06 AM
18. ### test question

At a large department store, the average number of years of employment for a cashier is 5.7 with a standard deviation of 1.8 years and the...

• Replies: 1
• Views: 5,878
10-17-2010, 11:18 PM
19. ### Expected Value Problem

The heights of all male students in a university have mean 170 centimetres and standard deviation 10 centimetres. Three male students are randomly...

• Replies: 12
• Views: 6,934
10-17-2010, 10:23 PM
20. ### Anderson-Darling test appropriate?

Hi, I have a large (>2500) number of z-scores and I want to test if the distribution of these deviates from a unit normal distribution. I have...

• Replies: 6
• Views: 11,867
10-17-2010, 10:04 PM
21. ### Describe Sample Space

Suppose you toss a fair coin until you obtain exactly R heads. 1) What is the probability that K tosses are required? 2) Describe your sample space....

• Replies: 2
• Views: 6,915
10-16-2010, 10:27 PM
22. ### simple probability question

Is the P(A and A) = P(A) ? If that's not clear enough I have a question that is: Given that a random case is either A or B what is the...

• Replies: 2
• Views: 3,031
10-14-2010, 06:55 PM
23. ### Probability Question

You randomly pick 10 marbles from a large bag containing 1/6 red marbles. a. What are the chances that you pick exactly 4 red marbles? b. If 10...

• Replies: 9
• Views: 4,306
10-14-2010, 03:10 PM
24. ### Pretty Basic probability question

Thanks guys. Figured it out!

• Replies: 5
• Views: 3,184
10-14-2010, 11:09 AM
25. ### Probability of 20-question test, binomial?

20 true-false quiz to determine who has read a book. Shes wants to choose the passing grade such that the probability of passing a student who...

• Replies: 9
• Views: 9,513
10-14-2010, 12:28 AM
26. ### Scaling covariance and variance

I have the variance and covariances for a number of assets(stocks), and i need to scale them from 1 month to a year. Would it be correct to think...

• Replies: 1
• Views: 7,334
10-14-2010, 12:16 AM
27. ### Probability HW

Hi, I need some help figuring out the inclusion probability. Here is the problem: Unequal probability sampling is often unavoidable, so it is...

• Replies: 0
• Views: 2,461
10-13-2010, 07:42 PM
28. ### 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: 13,980
10-13-2010, 05:20 PM
29. ### HELP! I brain cant solve it

I have tried this problem 100 time and I cant solve it . here it is Of six cars produced at a particular factory,3 are known to be defectives and 3...

• Replies: 2
• Views: 3,186
10-13-2010, 06:56 AM
30. ### probability , confusing table

I am really confused with the table , I am not sure if I am doing it right, Can you have a look at my answers? 3. In smoking related research,...

• Replies: 5
• Views: 2,693
10-12-2010, 07:23 PM
31. ### Is it Binomial?

I am really stuck with this question, I am trying to figure out which distribution it is , can someone give me a hint plz?:( 2. A physician is...

• Replies: 6
• Views: 2,985
10-12-2010, 06:53 PM
32. ### Plz HELP im stuck !!!!

Z=X+Y+2, W=X-Y Find f(z,w) >>> say Z=g(x,y) and W=h(x,y) then f(z,w)=double integral f(x,y)delta(z-g(x,y))delta(w-h(x,y))dxdy im stuch...

• Replies: 2
• Views: 2,633
10-12-2010, 12:27 PM
33. ### Question regarding Z Scale - Is my answer correct?

Here is the question. A company markets salmon in cans. It claims that the net mean weight of the cans is 8 and the standard deviation is .04. ...

• Replies: 2
• Views: 4,165
10-12-2010, 09:41 AM
34. ### System of 5 independent components

I have done problems similar to this one with 4 components but im getting stumped with this one. The probability of FAILURE for each components is...

• Replies: 8
• Views: 4,452
10-12-2010, 09:25 AM
35. ### Genotype probabilities

I'm having difficulty with this problem, although it seems easy. The possible genotypes of an organism are AA, Aa and aa (Aa and aA are...

• Replies: 1
• Views: 7,848
10-11-2010, 11:59 PM
36. ### Plase! I need urgent Help, MLE

hello i'm really stucked with this problem. hope anybody oould help me out. Thanks!!

• Replies: 1
• Views: 2,501
10-11-2010, 11:44 PM
37. ### Probability of combinations of events

Hello, I am trying to solve the following problem: We have a set of events and we know the probability of each event. We do not have values for...

• Replies: 2
• Views: 7,848
10-11-2010, 11:38 PM
38. ### Help with basic proportions

The Saloon claims that their pints, on average, are 16 ounces. To test whether the Saloon is actually pouring LESS than 16 ounces (at the .025...

• Replies: 0
• Views: 5,036
10-11-2010, 08:02 PM
39. ### Cumulative distribution help.

Okay so I've got this question: Let X be a random variable with a cumulative distribution function Fx. Prove that P(x=a) = 0 if and only if Fx is...

• Replies: 11
• Views: 6,010
10-11-2010, 06:25 PM
40. ### Probability of radar detection

Aircraft is in certain area, radar correctly registers its presence with prob. of 0.95. If it is not present, radar falsely registers its presence...

• Replies: 16
• Views: 11,517
10-11-2010, 02:39 PM
41. ### Help plz

Two RVs X and Y have the joint density f(x,y)=e^(-|x|-|y|) /4 Are these RVs independent? >> i can prove if they are independent or not by...

• Replies: 1
• Views: 2,221
10-11-2010, 12:19 AM
42. ### probability of expected mean?

Hey, so I've been having trouble with this problem. I'm not really sure what formulas to use or how to do it. Any ideas to help point me in the right...

• Replies: 1
• Views: 2,379
10-10-2010, 07:09 PM
43. ### P value two tail test estimation formula

Hi Thanks in advance for reading my question. For my stats class, we have estimate p value using the charts. And then we compare that outcome to...

• Replies: 0
• Views: 6,040
10-10-2010, 12:44 PM
44. ### Distribution using pmf

X=demand for the magazine with pmf x 1 2 3 4 p(x) .1 .2 .4 .3 Shop owner pays $1.00 for each copy of mag. and charges$2.00. If mags. left at...

• Replies: 1
• Views: 3,420
BGM
10-10-2010, 03:58 AM
45. ### Normal Distribution

try this guys, I only got 4 out of 9 trying :mad: Simply solutions would be generous:tup: I tried to solve these problems Z= (x-µ)/sigma but im...

• Replies: 1
• Views: 4,071
10-10-2010, 12:06 AM
46. ### ????HOW to decide Independance of 2 RVs thru joint density without calculation????

given the joint density:f(x,y)=(x+1)(y+1)/8, |x+y|<=1, |x-y|<=1 Find the boundries of the domain of these RVs before any calculations. Are...

• Replies: 0
• Views: 2,030
10-09-2010, 12:07 AM
47. ### Probability of Events - Accident Stats

I am trying to figure out the likelihood that a series of accidents is either indicative of a problem or not, in other words how rare is this series...

• Replies: 1
• Views: 6,010
10-08-2010, 05:27 PM
48. ### Probability density function

I have a problem on one part of the four parts of this question. Here it is: The probability density function of the time customers arrive at a...

• Replies: 5
• Views: 11,832
10-08-2010, 03:00 PM
49. ### Dependent normal distributions

I'm doing some stock market analysis for a personal project. If I have two stocks which generate returns which are normally distributed, what is...

• Replies: 4
• Views: 9,016
10-08-2010, 01:33 PM
50. ### Probability Mass Function

I am given that X follows the geometric distribution and asked to give the probability mass function for X^2. I know that the probability mass...

• Replies: 5
• Views: 4,992
10-08-2010, 11:23 AM
51. ### NEED HELP with joint density problem

Two RVs X & Y have the jiont density: f(x,y)=a, x^2+y^2<=1 Find the constant a. >>> HOW CAN I SOLVE THIS ???can i say that z=x^2+y^2

• Replies: 5
• Views: 3,349
BGM
10-08-2010, 12:48 AM
52. ### from Uniform random variable to Logistic

Given U~Unif(0,1) and X=s*ln(U/(1-U)), where s>0 is a parameter, I am hoping to get F(x), where F(x) would turn out to be a logistic cdf F(x) =...

• Replies: 4
• Views: 2,901
10-08-2010, 12:21 AM
53. ### Does 'among' mean conditional or joint probability

I've been given the following chart about ppl who went through drug treatment and about whether they were subsequently convicted years later with...

• Replies: 3
• Views: 3,804
10-07-2010, 11:57 PM
54. ### Probability Mass Function

I have a question about probability mass function. I understand the simple problems with a toss of a fair coin etc. I have a slightly more...

• Replies: 1
• Views: 4,192
10-07-2010, 11:23 PM
55. ### Probability question in section involving conditonal probability

With probability of 1/6 there are i defective fuses among 1000 fuses (i = 0, 1, 2, 3, 4, 5). If among 100 fuses selected at random, none was...

• Replies: 1
• Views: 7,046
BGM
10-07-2010, 10:42 AM
56. ### Expected Value Question

I have been given f(x) = c*2^x where x = 1,2, ..., N. First, I had to determine the value of c such that f is a probability mass function. This is...

• Replies: 1
• Views: 2,656
10-06-2010, 05:51 PM
57. ### A question on the Poisson process

Let N be a Poisson process with rate 1, T^{(\lambda )} be an exponential random variable with rate \lambda independent of N, and U^{(\lambda)} be...

• Replies: 3
• Views: 3,206
10-06-2010, 01:34 PM
58. ### need some probabilty help ASAP please

Hey guys need some help asap please, if i know the percentiles p10 p50 and p90 figures, which formula do i use to calculate the mean? cheers

• Replies: 2
• Views: 3,013
10-06-2010, 04:12 AM
59. ### Need help with a problem with Indicator Random Variable

A building has 10 floors above the basement. 12 people get into an elevator at the basement, and each of the 12 chooses one of the 10 floors at...

• Replies: 3
• Views: 8,934
10-05-2010, 07:24 PM
60. ### 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: 12,449
10-05-2010, 03:44 PM

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