Distribution Definition and 1000 Threads

This paper: http://arxiv.org/abs/1509.02832, The Age Distribution of Potential Intelligent Life in the Milky Way, estimates the age distribution of intelligent civilazations in the Milky Way. Unsurprisingly we rank somewhat below the advancement level of termites compared to your typical ET. It...

Homework Statement A charge distribution has the form ##\rho=-\frac{q}{4\pi ra^{2}}(1-\frac{r^{2}}{a^{2}})\exp(-\frac{r^{2}}{2a^{2}})##. Compute the total charge Q, the electric field E, the potential ##\Phi##, and the electrostatic energy W for this charge distribution. Homework Equations...

Homework Statement An experimenter measures the counting rate from a radioactive source as 10,150 counts in 100 minutes. Without changing any of the conditions, the experimenter counts for one minute. There is a probability of about 15 percent that the number of counts recorded will be fewer...

Homework Statement Let X be a continuous random variable with cumulative distribution function given by F(x) = P(X<x). Define a new random variable U=F(X). Homework EquationsThe Attempt at a Solution OK so to solve this problem I first say U=F(X). F(u)=P(F(X)<u) which means F(u)=P(U<u) is...

Homework Statement The Earth is constantly being bombarded by cosmic rays, which consist mostly of protons. Assume that these protons are incident on the Earth’s atmosphere from all directions at a rate of 1366. protons per square meter per second. Assuming that the depth of Earth’s atmosphere...

How is the expected frequency column worked out for each interval of trains? 2) My attempt Take the first interval, 60 - 62, I thought about doing this: (62 - mean) / standard deviation (62 - 67.45) / 2.92 = - 1.866 using Z score < - 1.886, from the normal distribution table, I get: 1 -...

hello every one , I want to know how we get phonon frequency spectrum theoretically by using three modes and dispersion relation, can anyone explain it. for example it is phonon energy correspond to density of state how it is obtain?

We know that If object is homogenius and small (like gold atom) we can use this equation to calculate total energy of object when it moves very slow due to speed of light.And the equation is ##1/2(m_1v^2+m_2v^2+m_3v^2...=1/2Mv^2##, ##(M=m_1+m_2+m_3...)## here v is small and we are talking about...

In one double slit experiment, one physicist placed a convex lens before the back screen detector. The individual photons passed through the double slit then through the lens. The individual photons then go through the focal point, then a good distance after they reach the focal point they hit...

Hi, I have a quick question. If both X and Y are uniformly distributed on the unit interval [0, 1]. Can we prove that the joint distribution of (X, Y) is uniform on the unit square [0, 1]×[0, 1]? Do we need any condition to ensure the result, such as Independence between X and Y? Thanks.

Never mind. I got this one. Couldn't figure out how to delete the post though.

Homework Statement Can we consider the universe to have a uniformly charged distribution? If so, shouldn't the field at any point in space be zero? Since the universe is infinite, will it be symmetrical about any point, field should be zero right? Why is this not true?[/B]2. The attempt at a...

Homework Statement An infinitely long cylinder of radius R is placed above an infinite grounded plane. The centre of the cylinder is a distance (d) above the plane, and the cylinder has a surface charge density of σ. (a) Initially ignoring the grounded plane, what is the electric field due to...

Homework Statement A ring of radius R has a current density ##\vec J=J(r, \theta) \sin \phi \hat \phi## where phi is the azimuthal angle in spherical coordinates. Calculate the charge distribution considering that it was initially null. Homework Equations Not sure. Maybe ##\nabla \cdot \vec J...

Hello, I've read in a paper that the following binomial distribution \sum_{k=floor(N/2)+1}^N{N\choose k}\varepsilon^k(1-\varepsilon)^{N-k} can be upper bounded using Chernoff bound by e^{ floor(N/2)}\,\Phi(s_0) where \Phi(s)=\left(1-\varepsilon(1-e^s)\right)^N and...

Hi all, in following the many available derivations of the Boltzmann distribution I was trying to do it by maximizing W, which is N choose n1,n2,...nt., instead of lnW, because it should give the same answer (since W is monotonically increasing with lnW, am I wrong?). So given the two...

This technically isn't a coursework or homework problem: I have a uniform Joint density function for the lifetimes of two components, let's call them T1 and T2. They have a uniform joint density function, both are positive it follows, and the region is 0<t1<t2<L and L is some positive constant...

Homework Statement This is not really a homework problem, it's a problem that I am working on and am not able to come to an end of it. The story is: I have a certain amount of force, let's call it ##F_0##, that I can distribute on a certain length ##L## just the way I want it to. Meaning that...

Hi, I have a problem in my program and I cannot figure it out. In the last post I had a problem about some arrays, I perfectly resolved it thanks to you, but now my problem is a little bit subtle. I have a subroutine(here I'll post it has a program )that generates random numbers in order to...

I learned that dark matter distrubition is homogeneius and isotrophic in cosmic scales. I searched some galaxies dark matter distrubition.And I am actually suprised. Why cause every galaxy has a different ratio of dark matter baryonic matter distrubition. In cosmic scales baryonic...

Hello all, Is there any lower bound on the following Binomial distribution \sum_{k=floor(N/2)+1}^N{N\choose k}\epsilon^k(1-\epsilon)^{N-k} as N goes to infinity and where epsilon is less that or equal 10^-3? Thanks

I need help understanding normal distribution. I am self studying statistics to help me in my role of teaching excel as a business tool. I understand taking a data set and creating a frequency distribution. I don't understand about normal distribution. Why should any data set regardless of...

Homework Statement Random variable X is uniformly distributed on interval [0,1]: f(x)=\begin{cases} 1 & \text{ if } 0\leq x\leq 1\\ 0 & \text{ else} \end{cases} a) Find probability density function ρ(y) of random variable Y=\sqrt{X} +1 I tried like this. Is it good, if no why not...

A test consists of 10 multiple choice questions with five choices for each question. As an experiment, you GUESS on each and every answer without even reading the questions. What is the probability of getting exactly 6 questions correct on this test? The answer is: $$\binom{10}{6} (0.2)^6...

Looking at another textbook problem, hope someone can let me know if I'm on the right track: Let $X_1, X_2, ... X_{25}$ be a random sample from some distribution and let $W = T(X_1, X_2, ... X_{25})$ be a statistic. Suppose the sampling distribution of W has a pdf given by $f(x) =...

What is the velocity distribution of evaporating H2O molecules? It can not be Maxwellian.

Homework Statement A sphere of radius R has a volume charge distribution ##\rho(r)## given by: ##\rho(r)= \rho_0 \left( \frac{r}{R_0} \right) \ \ for \ 0 <r<R## ##\rho(r)=0 \ \ elsewhere## Where ##\rho_0## is a constant. Use Gauss's law to find E field outside the sphere. Homework Equations...

Hey everyone, I'm hoping I can get some input on this. As some of you may recall, I'm currently in an internship at Fermilab, and I've hit a snag in plotting my data. I'm measuring the intensity of the NuMI neutrino beam at multiple different points to look for discrepancies in the measured...

Note: I have noted that one of the formulas I have provided does not show up on my webpage in preview mode and so have also made it as an attachment. Quick summary: I have found two different websites that offer the equation that I am looking for in different forms, but I am starting to think...

http://www.colorado.edu/physics/phys3320/phys3320_sp12/AJPPapers/AJP_E&MPapers_030612/Griffiths_ConductingNeedle.pdf I was reading this paper, and was confused by a result in section 2-A. (Heck they even mention they weren't expecting it themselves). The purpose of the paper is to find the...

hi i have MARSHAL-OLKIN exponential weibull distribution which have the following cdf and pdf.. how could i convert it to bivariate distribution? thanks

Hello, this is my first post and I've been out of school for a few years and now working a job in my field at a distribution utility, but I'm just really rusty or green on a lot of things now that I'm being challenged. Seems like the simplest questions elude me! Anywho, I've been tasked with...

I'm happy to find a forum such as this! I graduated college several years ago in electrical engineering, and last year finally landed a job in my field in distribution utilities! I like the challenge and using my degree, but I find myself having a lot of questions on how to do things. I don't...

Here is a question about probability density. I am trying to work it out using a different method from the method on the textbook. But I get a different answer unfortunately. Can anyone help me out? Question: Let X be uniformly distributed random variable in the internal [ 0, 1]. Find the...

derive f distribution as x1 and x2 are independent random variables having a chi-square distribution with n1 and n2 degrees of freedom.. aslo mgf and find raw moments ... and finds its mean and variance.?prove it ?help me guys?

I heard that the analysis of wave measurements close to shore verifies that as long as wave amplitudes are small with respect to mean depth a Rayleigh distribution remains satisfactory of wave heights, but how ?

If I pick up my Wife, who is in turn holding our Daughter, both me and my Wife feel the respective weights. Me of holding both, and my Wife of holding our Daughter. How is my Daughter's weight split between my Wife and I?

Hello My question could be about bars and litres/sec but I'll express it as volts and ampères, mathematically it's the same puzzle for me. How do you calculate the currents in circuits when there are devices whose resistances are not linear? In the following network there are 3 low value linear...

Homework Statement A gas consisting of 15,200 molecules, each of mass 2.00 x 10-26 kg, has the following distribution of speeds, which crudely mimics the Maxwell distribution: Number of Molecules - Speed (m/s) 1600 - 220 4100 - 440...

Homework Statement Given a semi-infinite stick (that is, one that goes off to infinity in one direction), determine how its density should depend on position so that it has the following property: If the stick is cut at an arbitrary location, the remaining semi-infinite piece will balance on a...

Homework Statement Random variable x is defined on interval (1,3) and it has probability mass function f(x) =A(x2 +1= a) Find PMF, g(y) for y=x2 b)Expectation of y c)Variance of y d)Distribution function of y. e)most probable value of y The Attempt at a Solution As far as a), i integrated from...

Hi, Where can I find a database with the mass distribution and its movement in the well-known universe? Best wishes, Jens

Homework Statement the distribution function: f(x)= x + 1 when -1 < x ≤ 0 -x + 1 when 0 ≤ x < 1 0 otherwiseHomework Equations The Attempt at a Solution on the first interval i found (1/2)x2 +x + c on the second interval -(1/2)x2 + x + c and when integrating the c's will cancel each...

The expression relating the mean number of molecules with velocities in the range v and v + dv and position r and r + dr is given by where n = N/V is the number density of molecules. My question is: Since LHS is an integer, how do we ascertain the RHS is an integer, since it involves pi and an...

Homework Statement [/B] While shooting at target, soldier shoots from machine gun fixed in a way so it can rotate only around z axis. deviation from center of target due to twitching of machine gun is random variable with Gauss distribution. Deviations are such that inside of 20m from center of...

While linear accelerating an electron, with direction of acceleration being the ##z+## axis of the spherical coordinates, its radiation in angular distribution form is(according to this tutorial: http://farside.ph.utexas.edu/teaching/em/lectures/node132.html) ##\frac{dP(t')}{d\Omega} =...

hello all.glad to be here! please in the attached document, column 5 and 6 which represents the differential and cumulative frequency distributions were obtained using equations (5) and (6). I'll be mighty grateful if anyone can give me a step by step breakdown of how it was done?? Many thanks...

I recently read that the charge density is less on surfaces with greater radius of curvature on the surface of a charged irregular conducting body . if anyone can provide a proof or explanation , please help!

Hi, I was trying to think of a way to generate a Poisson distribution using a single deck of 52. Say I am looking at the position of the Ace of spades in the deck after a number of shuffle rounds (1 shuffle round is 7 riffle type shuffles). Success is that an Ace of spades is on top of the...

Suppose the pdf is A*exp(-mv^2/2kT) , where A is the normalization constant. To obtain A I would integrate the pdf over the all possible values of v. The question is, should the limits be (-infinity,infinity) or [0,infinity) ? It seems that only by choosing the former can I get the correct...