Statistics Definition and 998 Threads

Homework Statement My task is to explain why the sample statistics I have obtained differ from the population statistics I have obtained from some data - using "concepts taught in class, if they exist". I have calculated x̄ and s, as well as σ and µ. Homework Equations First of all, the...

I'm a physics engineering student and I need to do a final project for my probability and statistics class related with my major. Can you help me with finding one? The problem is the only experiments I can think of are either unpractical or expensive (I have to pay for the materials): - after...

Can someone please explain how the standard deviation is relevant when we are talking Brownian motion? And why is statistics important when we want to understand the movement of a brownian particle?

Question from Jim on Yahoo Answers: The things you should know are: 1. The sum of normal random variables is a normal random variable with mean equal to the sum of the means and variance equal to the sum of the variances. 2. Multiplying a normal RV by a constant gives a normal RV with mean...

Homework Statement Assume z_1, ..., z_m are iid, z_i = μ+\epsilon_i \epsilon_i] is N(0,σ^2) Show that f(z; μ) = g( \bar{z}; μ)h(z) where h(·) is a function not depending on μ. Homework EquationsThe Attempt at a Solution Now z is normal distributed with mean my and variance sigma^2...

Hi. I'm reading an introductory section on the Bose-Einstein condensation of a non-interacting, spinless boson gas. I'm confused by the claim that the ground state is in a coherent state with eigenvalue sqrt(N0) exp(i theta), where N0 is the expected number of particles in the ground state. The...

Homework Statement I'm trying to study off an old practice midterm for my upcoming statistics midterm. The midterm is attached. Part One is the following problem: The effect of a new antidepressant drug on reducing the severity of depression was studied in manic-depressive patients at...

Homework Statement Let X1, X2, ..., X9 be a random sample from a normal distribution, Xi~N(6,25), and denote by Xbar and S^2 the sample mean and sample variance. Use the standard statistical table for normal distribution. Homework Equations E[S^2] = δ^2 = 25 S^2 = (ƩXi^2 -...

Homework Statement (From Probability and Statistical Inference, Hogg and Tanis, Eighth Edition, 5.1-5) The p.d.f. of X is f(x) = \theta x^{\theta - 1} for 0<x<1 and 0<\theta<\infty. Let Y = -2\theta \ln X. How is Y distributed? Homework Equations Um... Fundamental Theorem of...

Hello. Am I counting right with these problems? I can't remember exactly how they were worded, but I remember what they were asking... 1) Given 20 men and 20 women, how many groups of 12 can you make with 6 men and 6 women. I said 20.Combination.6 * 20.Combination.6. 2) given S= {1, 2...

I´m wondering how to find out something about distribution functions after I´ve calculated the scewness. I have 15 numbers, mean is 3.206, highest is 7.028 and lowest is 0.9209. Variance is 2.958195. I calculate the skewness and got 0.945. I´m wondering which of the following distributions is...

How do I calculate least squares? The way it's described is confusing to me. \hat{β}= r* sy/sx . sx and sy is the standard deviation of x and y, correct ? So let's say I have sets of numbers such as (16,19),(18,17) etc... 16 and 18 would be x and 19 and 17 would be y. So I have to calculate the...

Hi. I work with rain (precipitation) time series, and would like to extract time statistics: - precipitations per month - precipitations per year - precipitations per month and year - precipitations per hour - precipitations per month and hour - mean precipitation, deviation, ... I...

Homework Statement Suppose that the weights of airline passenger bags are normally distributed with a mean of 48.14 pounds and a standard deviation of 3.71 pounds. Let X represent the weight of a randomly selected bag. For what value of c is P(E(X) - c < X < E(X) + c)=0.95? Give your answer...

I'm about to finish my lower division math requirements, which will cover everything for all my lower division coursework for all three subjects, bar 3 programing coures, one that can be taken next quarter, and the other 2 which can be taken concurrently in the beginning of next quarter. If I do...

Given the fact that X and Y are independent Cauchy random variables, I want to show that Z = X+Y is also a Cauchy random variable. I am given that X and Y are independent and identically distributed (both Cauchy), with density function f(x) = 1/(∏(1+x2)) . I also use the fact the...

A1 Computer has 15 tablets stocked, but four of them were actually defectives. A client bought two tablets from A1 Computer. If both of them are good, things are fine. If the client gets one defective machine, A1 Computer will replace it and give a $100 rebate to the client. If the clients...

In 2007, 52% of all immigrants to Canada were females, 25% were under 18 years old, and 12% were females under 18 years old. a. Find the probability that a randomly selected person who immigrated to Canada in 2007 was a female and over 18 years old. b. Find the probability that a randomly...

Statistics: Question about "mild" and "extreme" outliers. I am studying statistics, and have noticed the definitions of the mild and extreme outliers. Mild outlier: Between 1.5q and 3q away from the nearest quartile, where q denotes the interquartile range. Extreme outlier: More than 3q...

Homework Statement Ive two questions not directly relating to a problem but just stat in general. i) In Swedish what is called the "help variable" for a regression equation: y=u'*B where u' is the vector of explaining variables (x1,...,xn) can apparently be written in many ways.. One...

Homework Statement I've attached both the problems into one image to make life easier since problem 1 has a diagram and the other does not. Homework Equations Bayes Theorem : P(A|B)P(B) / [P(A|B)P(B) + P(A|B')P(B')] B' = B Complement The Attempt at a Solution well for the first one i don't...

Homework Statement 1) A computer firm presently has bids out on three projects. Let Ai = {awarded project i} for i = 1,2,3. Suppose that P(A1) = 0.20, P(A2) = 0.25, P(A3) = 0.28, P(A1∩A2) = 0.10, P(A1∩A3) = 0.06, P(A2∩A3) = 0.08, and P(A1∩A2∩A3) = 0.01. Compute the following...

Homework Statement A random variable X has three, and only three, possible values, 0; 2; 4 with the following probability distribution: Probability: Getting a 0 is 0:7 Getting a 2 is 0:1 Getting a 4 is 0:2 Let X1 and X2 be two independent random variables with this distribution. (a)...

BLS has released data on unemployment for the month of January. http://www.bls.gov/news.release/pdf/empsit.pdf What I want to ask about is a blog from Karl Denninger on market-ticker. http://market-ticker.org/akcs-www?singlepost=2858099 He states that he used the "correct adjustment"...

I've calculated the mean difference of my (normally distributed) data set. The mean difference is defined as: Now, I'm trying to calculate the "mean difference deviation" in order to generate a confidence interval for this quantity ( "95% of the differences in the set are greater than...

hey guys, some hopefully easy stat questions if you will Im wondering about translating one statistical distribution to another, like going from: Bin(n,p) to N(np,sqrt(npq)) where q=1-p or that Po(au) is roughly equal to N(xu,sqrt(xu)) Im mostly sitting scratching my head on which...

Does anyone have sources on how many PhDs of each field is being produced each year? i.e. how many physics PhDs graduate each other, how many in mathematics, etc.

Homework Statement Find an efficient estimator for q(\lambda) := e^{-\lambda} in a Poisson model. (note: the efficient estimator is the one who reaches the Cramér-Rao lower bound) Homework Equations The Cramér-Rao lower bound: Let T be an unbiased estimator for q (as defined above), then...

What are the "natural" generalizations (if any) to Bose and Fermi statistics? fermions: 1 particle per state Bosons: unlimited number of particles per state do people consider things in between like states with a capacity n? are there other generalizations of these statistics? Thanks!

Hi everyone! Lately I have been trying to improve my typing speed, and have been playing a game called Type Race, where you type various short passages (the passages are selected at random from a text bank) and your score in WPM is recorded. What I want to do is determine whether or not my...

Suppose that IQ scores have a bell shaped distribution with a mean of 104 and a standard deviation of 14. Using the empirical rule what percentage of IQ scores are less than 76? Please do not round your answer. So far this is what i have 76 -104= -28 -28 __ = -2 14 *How do I...

Integrals of Expeced Value For Normal Order Statistics 1. Find the expected value of the largest order statistic in a random sample of size 4 from the standard normal distribution. Homework Equations E(X(4,4))=4∫xf(x)(F(x))^3dx, (from minus infinite to plus infinite), where f(x) is the...

Hello, I've just began my first probability class, and let me tell you, it's a doozy. It reminds me a lot of my physics classes: There's a general sort of way to go about solving a problem, but each problem is completely different from the other. If this was the entire major, I'd stop here...

So I have the option of either taking a year long sequence in probability theory or a year long sequence in mathematical statistics. Both require real analysis so both will be at the 'measure theoretic' level. I'm interested in these classes as they relate to computer science and specifically...

(This question was previously posted to sci.math.research. I only received one reply; sadly the advice therein conflicted with section 9.1 of H.A. David's "Order Statistics" - and probably with the fact that there was such a field of study as "r-extreme order statistics" - hence my reposting it...

Homework Statement http://img687.imageshack.us/img687/7963/screenshot20120102at185.png Homework Equations The Attempt at a Solution I understand how to compute a Chi-squared test, but I'm a bit confused about the wording of parts a) and c). Could someone possibly simplify it for...

Would you say that these "salary by degree" statistics are accurate? http://www.payscale.com/best-colleges/degrees.asp I know it's rude to ask people how much they make, but if you guys don't mind, could you at least tell me if these numbers are realistic, compared to what you've seen? This...

Hallo, I posted this in General Math, and I decided to post it here also because this room seems more appropriate. The formulas and part of the text are quoted from "Klimontovich - Statistical theory of non-equilibrium processes in a plasma": Let N_{a}(\textbf{x},t)...

Homework Statement So my HW is 27. Assume the heights of high school basketball players are normally distributed. For boys the mean is 74 inches with a standard deviation of 4.5 inches, while girl players have a mean height of 70 inches and standard deviation 3 inches. At a mixed 2-on-2...

I'm looking for a great formulay for statistics? Maybe along with a quick explanation for each formula.. there are so many for different scenarios that I find it confusing. Like for : Conditional probability and independence, random variables and expectations, binomial and related...

Is there any evidence for quantum fermi-dirac distributions among neutrinos, besides the obvious fact about their spin? I was wondering how Pauli exclusion principle would work with a neutrino 'gas', and what kind of quantum numbers they could have. It has been expected that if we ever did...

Homework Statement 1) A point (X1,X2,X3) are is chosen at random. X1-3 are uniform distributions across the interval [0,1] Determine P[(X1-.5)2 + X2-.5)2 + X3-.5)2 ≤ .25] 2) X and Y are random variables with the joint pdf: f(x,y) = 2(x + y) for 0≤x≤y≤1, 0 otherwise. Find the pdf of Z = X + Y...

Homework Statement Hello, I have some data from a statewide standardized exam, and I am trying to do a regression model, but am having a bit of trouble. (Im a mathematician and not a statistician). Basically, I am trying to show some type of correlation between race and test scores...

Hi, Can anyone point me to the pdf, cdf, moments, etc of y = sinc(x) = sin(pi*x)/(pi*x) where x ~ N(0,s^2)? Thanks!

Hi, I have to work with Expected Values and I am extremely confused over the following: In the part of my book that teaches me about Probability Distribution, in order to calculate the Expected Value I have to: Lets say we toss a coin twice. We can get 0 Heads, 1 Heads or 2 Heads I then draw...

I see this all the time, but I just want a simple explanation of what parametric, and nonparametric statistics means! Thanks so much.

I've read a lot of posts, and think it might be helpful to point out some facts that I think would help clarify people's arguments. 1. Income is not wealth. Using one as a proxy for the other is like using velocity as a proxy for position. A small disparity in income, acting over time...

Homework Statement I'm doing a past paper for my statistics course, and there's no provided solutions. I want to know if my attempt is correct. This is part of the paper: Homework Equations N/A The Attempt at a Solution i) Q0 = 1.06, Q1 = 1.335, Q2 = 2.04, Q3 = 2.275, Q4 = 2.64 ii) IQR = Q3...

Homework Statement Two different types of injection–moulding machines are used to form plastic parts. A part is considered defective if it has excessive shrinkage or is discoloured. Two random samples, each of size 300, are selected and 15 defective parts are found in the sample from machine...

Homework Statement Consider the bivariate density f(x,y)=c(x+y) for 0<=x<1, 0<=y<1 a) Obtain the appropriate normalization constant c. b) Obtain the marginal densities for X and Y, and calculate their means and variances. c) Obtain the covariance between X and Y, and check whether the...