Mean Definition and 1000 Threads

Homework Statement A diet pill is given to 9 subjects over six weeks. The average difference in weight (follow up - baseline) is -2 pounds. What would the standard deviation have to be for the 95% T confidence interval to lie entirely below 0? ANSWER: Around 2.6 pounds or less Refer to the...

Homework Statement What is the mean free path of an N2 molecule in an ultra-high-vacuum chamber at a pressure of 10-10mbar? Homework Equations λ=1/(√2)nσ number density n, collision cross-section σ p=nkT pressure p, temperature T σ=πd2 d molecular diameter The Attempt at a Solution...

Homework Statement Derive an expression for the mean collision time in a gas where the collision cross-section is σ and the number density is n. The Attempt at a Solution I'm just using my book to do this, and I can't get past the first bit... It says Consider a particular molecule moving at...

Homework Statement If Y=X1+X2+...+XN prove that <Y>=<X1>+<X2>+...+<XN> Homework Equations <Y>=∫YP(Y)dY over all Y. The Attempt at a Solution I only seem to be able to show this if the Xi are independent, and I also think my proof may be very wrong. I basically have said that we can write the...

In NBA, Announcer says "foul to give" at the end of the game, please some one explain. when will "foul to give" will be used? i mean, at which quarter of the game? & also A team has 3 fouls left, can they foul B Team without getting penalty is meaning of "a foul to give"? can shooting fouls...

http://www.pluggakuten.se/wiki/images/3/3e/Prov221.JPG Solution

Go to 1:24 of this video: He recalls some integral he wrote at a young age: " ... times the sixty-fourth power of ... what?" and looks confused. At 1:44 Neil Degrasse Tyson says, "By the way, the answer to your little calculation is i." Can someone explain the historical reference to me...

Dear Friends! Is weighted mean greater than mean? Actually i need to prove (c-b)f(a)+(b-a)f(c)>(c-a)f(b) when when f is continuous and strictly increasing in [a,c],where a<b<c.

Homework Statement What exactly does it mean for a surface to span a contour/curve? For example, which surface(s) span the contour/curve defined by the equations x^2 + y^2 = 1 and z = y^2? Homework Equations N/A The Attempt at a Solution I'm not sure if I'm saying something nonsensical, but...

If I built up static in me and then touch a doorknob and get shocked, am I then sufficiently grounded to be able to touch electrical components? Or was it just that the extra electrons were discharged and I should still ground myself in another way before touching electrical components?

Hi Guy, My name is John Dolan and I am an Irish student studying Astronomy in the university of Groningen in the Netherlands. I have been interested in Physics and Astronomy since I was knee high to a grasshopper and I look forward to asking questions, finding out new ideas and new ways of...

http://www.iflscience.com/physics/physicists-develop-reversible-laser-tractor-beam-functional-over-long-distances In this article, they said they could control the particle's direction by changing the laser's polarization. Could someone explain this to me? I have to do a presentation on it...

http://web.phys.ntnu.no/~ingves/Teaching/TFY4240/Exam/Exam_tfy4240_Dec_2013.pdf solutions: http://web.phys.ntnu.no/~ingves/Teaching/TFY4240/Exam/Solution_tfy4240_Dec_2013.pdf In problem 3 a) I'm supposed to reform the integrand from ##\vec{J}(r',t_r)## to something like ##\vec{J}(r'|\omega)##...

It would be better with a clear example to understand

Scores on an examination are assumed to be normally distributed with a mean of 58 and a standard deviation of 18. (a) What is the probability that a person taking the examination scores higher than 72? (b) Suppose that students scoring in the top 10% of this distribution are to receive an A...

Hello, I've been reading astronomy books for some time now but after leaving things for a while I seem to forget rotation directions. For example, I know that the Earth spins in the anticlockwise direction. That is easy to see why. They say that motion of the Earth is eastwards. Because of the...

I am having trouble deciphering the opening gambit of an explanation of mean values of functions. It begins as follows: "Consider the part of the curve y = f(x) for values of x in the range a ≤ x ≤ b." A graph is shown with a curve cutting the x-axis at c with a shaded positive area bounded...

I'm not a physics person (just an interested layperson) and have read that quantum particles don't have any location until they are measured. First, is this true? And, if so, what does that mean? For example, if you don't know where a particle exists, then how can you even measure it? And...

If you write a=dv/dt Then you can write it as dv=a*dt And take the integral on both sides integral(dv)=integral(a*dt) My question is: What does dv=a*dt mean?? How do I interprete it? What does the individual term dt mean? And what does dv for it self mean? To me it seems like “dv” means...

I'm new to physics and I see "det" used in math a lot. What does it mean?

The loggamma distribution is defined by $$ g(x) = \frac{1}{ \Gamma ( α) θ^{ α} } \frac{(ln( x))^{ α - 1}}{x^{1+\frac{1}{θ}}} $$, for $$ 1 < x < ∞ $$ where α is a positive integer. I've been trying to find the mean and variance of this distribution. It's been somewhat frustrating because the...

Hello All, Pertaining to General Relativity, what do we mean when we tell a space is flat or space is curved? Is it that sum of the angles of a triangle = 180? Or is it something else. I was listening to a lecture of Prof.Susskind, when he takes a piece of paper, makes certain points on the...

I did the problem but none of my answers match up with the answer choices so I'm obviously doing it wrong. Can someone show me how to do these two problems. I have a test coming up and I am so behind For women aged 18-24, the systolic blood pressure (in hg mm) are normally distributed with a...

Homework Statement The components of a random vector ##\mathbf{X} = [X_1, X_2, \ldots, X_N]^{\intercal}## all have the same mean ##E_X[X]## and the same variance ##var(X)##. The "sample mean" random variable $$ \bar{X} = \frac{1}{N}\sum_{i = 1}^NX_i $$ is formed. If the ##X_i##'s are...

Homework Statement Hi, I am doing some basic X-ray analysis and trying to quantify the measurement uncertainty associated with my determined value for the K-α line of copper. I have obtained the x-ray spectrum from a copper target using a detector and multichannel analyzer (No. of pulses/pulse...

Homework Statement (We are to solve this with Monte Carlo programming. Based on the universe from Olber's paradox) Suppose you are in an infinitely large, infinitely old universe in which the average density of stars is n = 10^9 Mpc^−3 and the average stellar radius is equal to the Sun’s...

Could anyone explain what the following ratings mean on a transformer? 120kw load, 1000v/500v, 60Hz

While I am familiar with the derivation of the relationship between mean translational kinetic energy, ##<E_k>##, and temperature, ##T##, for an ideal gas (namely ##<E_k> = \frac{3}{2}k_B T##); I fail to see how we can establish such a relationship for solids, liquids, and even real gases. Could...

I'm studying electrostatics and magnetism right now in Physics II for Engineers. I'm doing ok with most of the concepts, doing well in class, etc. I'm missing (or at least not 100% sure) of a basic part of the concept here. I feel like I'm correct in assuming that an object with no charge is...

Hi guys, I'm getting ready for a stats exam and one of the questions looks like this If I'm not given a histogram, how can this be solved?

Hello, everyone. What do the blue and pink color the rust indicator shown mean? Let say, the mixture of potassium hexacyanoferrate(III) and phenolphthalein is the rust indicator. And we use to detect the rusting of an iron nail. And the result is: the tip, head region of the nail appear blue...

Homework Statement Determine the minimum mean square error for the joint PMF. You will need to evaluate ##E_{X, Y}[(Y - 14/11\cdot X - 1/11)^2]##. Homework EquationsThe Attempt at a Solution The answer is ##\frac{3}{22}##, but when I work it out, I get ##\frac{203}{484}##. From my values, I...

Need help with this exercise been stuck on it for a while i think i get the gist of what i am supposed to do but can't seem to get it to work i am definitely missing something. I set h(x)= x-2/3 - g(x) and tried using the mean value theorem on [a,b] and then tried finding the minimum value of...

The Squeeze Theorem states that if three functions f(x), g(x), and h(x) exist, and f(x) \leq g(x) \leq h(x), and if \lim_{x \rightarrow a} f(x) = L and \lim_{x \rightarrow a} h(x) = L, then \lim_{x \rightarrow a} g(x) must exist and its value must be L. Here is something I don't understand...

Sigh. A couple of days ago my first paper got rejected. The editors claimed that " the experts we consulted felt that the paper is not suitable for the journal". A few days later I wrote them back requesting them to elaborate on where my paper had failed to meet their expectations and that any...

This is problem 20b from chapter I 4.10 of Apostol's Calculus I. The geometric mean $$G$$ of $$n$$ positive real numbers $$x_1,\ldots, x_n$$ is defined by the formula $$G=(x_1x_2\ldots x_n)^{1/n}$$. Let $$p$$ and $$q$$ be integers, $$q<0<p$$. From part (a) deduce that $$M_q<G<M_p$$ when...

Hello, I were wondering how to say the unit of the momentum by words, for example if the momentum equals 15 GeV/c , is it right to say: The momentum is 15 giga electron volts divided by the light velocity ? will this be clear for an audince, since ' c ' here can equals 1 at natural units ...

Hello! (Wave) In order to show that not every collection of objects is a set, we do the following: We will show that if we suppose that "everything is a set", we are lead to contradictions. If $V:=\{ x: x \notin x \}= \text{ the collection of all objects, that don't belong to themselves }$ ...

say you have <ψ|x|ψ⟩ or <0|F|k⟩ where F is an operator, what does this actually mean? I understand C|ψ⟩ would be the operator C acting on PSI and <ψ1|ψ2⟩ is the inner product of two wavefunctions but what would a third term inbetween them mean? thanks for any help

In an equation, there was an Ept (just those letters) embedded within that equation, does anyone know what it means? LaTeX code doesn't seem to be working either.

I'm filling out a grad application to Berkeley, and one of the forms has the title "Publications and Presentations" and asks I have no publications and I haven't given presentations in the context of a conference or the like, so it seems reasonable to leave this blank. However...

I have an experiment in which I want to extract the distribution function of a process. I expect it to be Gaussian. Each data point measured is an entire distribution, f(x), but I am forced to average over many points such that the result of the experiment is the sum of many measurements of...

What does the "r" in the formula F = - GMm/r^2 mean? Does it mean distance between the two bodies or the radial displacement ? Is the "r" a vector or a scalar?

Hey gang, I was wondering if there is a non-parametric version of the single set TTest? I know that often people refer to the Wilcoxon signed-rank test, but my understanding is that only tells you about the median, correct? Is there an equivalent that deals strictly with the mean? Cheers!

Hi, I am having trouble with this concept... "A mean speed (c) is calculated by multiplying each speed by the fraction of molecules that have that speed, and then adding all the products together. When the speed varies over a continuous range, the sum is replaced by an integral. To employ...

It is an option on the multimeter, I have read a little bit saying it has to do with transistors and it is a "test" for it...

I have a multimeter and for the "ohmeter section" for resistance it goes from a range of ~ 200 Ohms to 2000 kilo-ohms and then says also... Max. Open Circuit Voltage: about 3V Overvoltage protection: 250V AC Thank you in advance

$$\text{Consider the following decomposition of the time series }{Y}_{t}\text{ where }{Y}_{t}={m}_{t}+{\varepsilon}_{t},\text{ where }{\varepsilon}_{t}\text{ is a sequence of i.i.d }\left(0,{\sigma}^{2}\right)\text{ process. Compute the mean and variance of the process }{\nabla}_{2}{Y}_{t}\text{...

When I see something like "Humans and Bananas share 50% the same DNA with one another!", I have several questions. First of all, a banana has 530 million base pairs whereas a human has approximately 3 billion. Even if we took the first 530 billion base pairs of the human genome, this would only...

Homework Statement Radioactive nuclei are produced in an irradiated sample at the rate of 10 s-1. If the number in the sample builds up to a maximum of 1000, calculate the mean life and the half-life of the radioactive nuclei Can anyone advise on this one not sure how mean life is found...