statisics

  1. T

    Help with model Matrix GLM

    Hey guys been browsing the forums for a while, and usually find what I need! This is a tad more specific though so Ive made an account!! I've been puzzled by the form of the model for a while.. The model states that the response depends upon y~smoke + drink +smoke:drink +age:smoke. The model...
  2. B

    Could you please suggest a newbie about publishing Statistics related papers?

    Hello, I am quite new in writing and publishing papers. I have written a few papers, not that tough ones statistically, may be, but well written with properly performed analysis. One paper is on nutritional aspect of the country using a nationally representative data. There I have used a...
  3. M

    How to determine the accuracy of three combined tests

    Hypothetically, I have three tests that can determine if someone has cancer or doesn't have cancer. A True positive would indicate that the person doesn't have cancer. Below is a description of each test. Test 1: TP=.7 , FN = .3 , FP= .1 , TN = .9 , Accuracy = 80% Test 2: TP=.8 , FN = .2 , FP=...
  4. R

    Delta method

    I was wondering if anybody can help me as I've been stuck on this problem for ages and my attempts seem to all be incorrect so far. I have four estimators (W,Χ,Y,,Z) and standard errors for each. How can the standard error of D be cacluated from the following equation, where K, and L are...
  5. G

    One Factor Repeated Measures ANOVA questions

    Hi all, I have conducted a repeated measures ANOVA that has one factor with two levels. I also have a one between-subjects factor that has been taken into account. The results have come back to say that there is a significant difference between the within-subjects factor. My question...
  6. Z

    How do I interpret regression coefficients when there are log transformations?

    Hi, I'd like to know how to interpret with percentage the slope coefficients of a regressoin when I have: A- log(Y) ~ log(X) b- log(Y) ~ X c- Y ~ log(X) So far I found this web site, but I'm not sure it is accurate: http://www.ats.ucla.edu/stat/sas/faq/sas_interpret_log.htm...
  7. V

    What test to compare bacterial growth in three areas with repeating variables?

    I have a dataset of number of bacterial colonies grown from 11 water samples taken from 3 different watersheds. I want to know if the land area, population, number of waste water treatment plant outfalls, and number of septic tanks in the watershed have any effect on the bacterial growth. The...
  8. E

    finite Mixture of exponential in matlab

    Hi all can any body here help me with ((finite Mixture of exponential in matlab)) I want to simulate it in matlab or R for any given data ?
  9. M

    Chi squared troubles

    Okay, so i have been given an assignment in uni were they give us a set of data and we have to write up a scientific report. I have to perform a chi square test on the results in the hopefully attached table. I'm unsure about a couple of things: 1. Are my expected results obtained by using...
  10. M

    Is non-parametric test necessary for independent Likert-type items?

    Hi everyone I am having a difficulty in extending my survey analysis containing Likert-type item/questionnaires. I'll try my best to give a detailed overview of how my findings and analysis have been doing up to this point. The purpose of my survey is to determine the most important signage...
  11. D

    How to find the Cov(estimated beta0,estimated beta1)?

    Hi, i wonder how to find the Cov(estimated beta0,estimated beta1)? Thanks!
  12. M

    Tricky problem about 9 houses

    Ace Home Inspectors inspect nine houses each business day. Because AHI has been keeping records for several years they know that the probability of all nine houses passing inspection in a single day is 70%, the probability of eight houses passing on a single day is 20%, of seven houses...
  13. J

    non-central chi-square distribution.

    If X_i is distributed as normal with mean \mu and variance-covariance matrix D,where D is the diagonal matrix, then show that X^TD^{-1}D is distributed as noncentral \chi^2 with k degrees of freedom and noncentrality parameter \mu^TD^{-1}\mu=\lambda.
  14. J

    What will be the transformation and Jacobian of transformation for the following case

    Let X_i\sim N(\mu_i,\sigma^2) ; where [i=1,2,\ldots,n] show that \bar X and (X_i-\bar X) are independent. If all X_i had same mean \mu then we transform the random variables X_i; [i=1,2,\ldots,n] to Y_1=\bar X Y_2 =X_2-\bar X Y_3 = X_3-\bar X \vdots Y_n = X_n-\bar X...
  15. J

    Cumulants of non central chi-square distribution

    Cumulant generating function is defined by logarithm of Moment generating function. K_X(t)=\log M_X(t) let X is a non central \chi^2 variate with parameters degrees of freedom,n and non-centrality parameter,\lambda. Moment generating function of X is...
  16. J

    An Exercise of noncentral [math]\chi^2[\math] distribution.

    An Exercise of noncentral chi-square distribution. Let Y_1,\ldots,Y_n be independent random variables with Y_k distributed as N\sim(a_k,\sigma^2) , and \bar Y=\sum_{k=1}^{n}\frac{Y_k}{n} denote the sample mean, S^2 denotes the sample variance. Then show that...
  17. S

    OC Curve Program

    One of my friends has asked me to help him write a program to calculate the "n" and "c" values (sampling size, accept number), only given alpha(confidence level) , beta(probibility of acceptance), p1(AQL) and p2(LTPD). I'm currently a computer science major that has taken a few statistics...
  18. U

    Normal distribution theoretical moments

    how we can show that the follwoing equility holds E[(x-\mu)\sigma]=0 E[(x-\mu)^2\sigma^2-1]=0 E[(x-\mu)^3\sigma^3]=0 E[(x-\mu)^4\sigma^4-3]=0
  19. A

    Help with real estate statistics.

    I am a real estate appraiser in California. I want to conduct a study that will tell me what certain aspects of properties, like bedrooms, square footage, garages, pool, etc. Our multiple listing service that I will be using allows me to export all the physical characteristics of a home to...