1. M

    What is normal curve actually?

    Hi All, I am fairly new to Stats and thus this question. I was going through different materials to learn stats. 1. Somwhere its mentiond that a population, if plotted against frequency on a bar graph can produce a normal curve (e.g popcorn popping, heights of people etc) 2. Whereas somewhere...
  2. V

    Calculating Cauchy's PDF, using domain definition drawings of F_X/Y(z)

    Hi, I am trying to draw F (CDF of Cauchy) using X/Y relation for X,Y~N(0,1) iids and at some point very shortly I get lost. Especially because I don't know if I'm on the right direction. Could you direct me to the right way of solving this using the way I chose? So. Problem: Given X,Y~N(0,1)...
  3. S

    Probability Mass/Density Function

    Hi, I have a matrix of 24x15500 (time x no.of occurrences of an event). The number of occurrences is in the form of binary (0/1). I took the percentage of occurrence for each time, so I ended up getting the following 24x1 matrix. 1 0.999935612645676 1 0.994913399008435 0.973150473247054...
  4. F

    How to extract/import a PDF table in a data frame?

    To extract a PDF table in R I have used the pdftools package: library(pdftools) txt <- pdf_text("Downloads/Bac-2016.pdf") The extracted table I can see as a plain text with: cat(txt) The question is how to import this plain text table in a data frame? My OS is Ubuntu 16.04 * Introducing...
  5. F

    Change variable PDF with less variables than before

    My question is very simple, I have a probability density function that depends on four variables p(x1,x2,x3,x4). Now each of those variables depend on three new variables, i.e xi=xi(y1,y2,y3) so I want to find the new PDF given by p(y1,y2,y3). The problem is that the jacobian of this...
  6. B

    Probability Density Function of the derivative of a stochastic process

    Dear all; What is the expression of the PDF of the derivative of a stochastic process? My problem is completely general and theoretical, so, let's assume that all statistics of the stochastic process are given (e.g. pdf, higher order statistics, and so on). In other words, if we know...
  7. B

    Standardizing monthly sales figures in excel

    Hi everyone, this is my first post. In excel, I have approximately 723 rows of sales figures, broken down by month. I have an average monthly purchase (in Dec. 2014) of $24,500.47 and standard deviation of $76,232.24. The problem is, many of the rows have a $0 purchase (that member didnt...
  8. G

    Big rounding error in R or miscoding? Pdf of a quadratic of function of N(0,1)

    Dear all, I am trying to plot the pdf of a random variable y defined by : y=c+b*x+a*x^2 The pdf is a non-central chi-squared distribution. For a>0, it should be equal to zero if y<d, where d=c-(b^2)/4a (see attachment for the details). Strangely enough, when computing it with R, the pdf...
  9. S

    Is it possible to plot pdf from moments ??

    Hi guys, I'm a mechanical engineering student and new to statistics. I'm facing a little bit of a problem with pdfs. I have used the Quadrature Method of Moments to find 6 moments of an unknown particle size distribution function. I'd like to know if there is a way to plot the distribution...
  10. I

    Summing Uniform Distributions

    Hi, I can't seem to work out (or find anywhere) how to add two independent uniform distributions. My problem is as follows: I have random variable X~Unif(0,13), and error Z~Unif(-0.5,0.5) which is independent of X. I need to find Y=X+Z, the joint pdf of X and Y, as well as the...
  11. C

    Plotting the pdf of a negative binomial distribution using mean and stnd deviation

    I have been using a negative binomial distribution to describe my data; in order to allow me to randomly sample from the parameterised distributions. I have had no problems getting r (the number of successes) and p (the probability of success) for my distribution. My problem is that I would like...
  12. S

    Comparison of average values of data sets

    Hi, I want to know if mean of A>B and A1, A2 are the two subsets of A. Similarily, B1, B2 are two subsets of B. Is the condition A1<B1 and A2<B2 mathematically possible????? As I think it is not. I think that either both or at least one subset must have shown the same relationship in their...
  13. T

    Stochastic Model Validation

    Hi, I am working on a model that takes in a stochastic time series (turbulent velocity) as input and produces n time series outputs. Since the inputs have a stochastic component, every ensemble (or every run of the model) produces slightly varying outputs. Now I want to validate my model by...
  14. S

    Method of Moments

    Question: Let X1, X2, ... , Xn be a random sample of size n from a population with pdf f(x;theta) = [3(theta - x)^2] / (theta)^3 from 0 < x < theta and zero otherwise. Use the Method of Moments to find a point estimator for theta.
  15. F

    Parzen Window

    Hello, Is there any newer or better method (instead of Parzen) for estimating a probability density function from a set of data? for example can we use Copula? Thanks
  16. B

    Order Statistics Problem

    Hi there I have random variables X1,X2,X3,...,XN which are I.I.D. Each of these random variables are Erlang Distributed. X=min{X1,...,XN}. Now the sample size N changes with each iteration according to the following rule If Yn<=X<Yn+1 Then N=2^n where n is an element of...
  17. H

    E(X), bag with 6 red and 5 black balls, X = number of red balls

    A bag contains 5 black and 6 red balls. Two counters are drawn, one at a time, and not replaced. Let X be "the number of red counters drawn". Find E(X). ive drawn up a tree diagram which im assuming is correct EDIT: Below is the corrected tree diagram, as eagle eye Dason had spotted a mistake...
  18. Z

    Very long post - need help thanks

    Dear All, I am writing to you because I have got a lot of troubles with some concepts regarding Generalised Linear Models. I need to understand it by the January 2012. I hope it is possible. I am currently getting through one of the books regarding generalised linear models in a pretty much...
  19. S

    probability density function

    hi, can any one let me know with example "probability density function". I understand in more details about PDF with exaple. please help me
  20. T

    math to compute width of gaussian PDF(x) given sigma & N values of random variable x

    Hi Experts, I'm working in industry and have an application requiring some expert knowledge on statistics/probability. I have a probability distribution function (PDF) for a Gaussian random variable. I know the standard deviation of the PDF. I also know total number of experiments conducted...