simulation

  1. L

    I need someone to write me a basic code please!!

    Hi, I am learning basic programming with R, and I desperately need someone to write me a PSEUDO code and code for it please: Here's the situation "you have been sentenced to die tomorrow, but you're offered a way out... you get given 12 red balls and 12 blue balls together with two urns...
  2. trinker

    Correlation pvalue from a bootstrap

    I'm working through some machine learning stuff that deals with simulation/bootstrapping and come across a point where a pvalue is calculated but not how it was calculated. This is precisely the type of work I'm moving towards so I want to understand how to do it. Here's what the author of the...
  3. C

    Improved Monte-Carlo method vs. hit-and-miss method

    I am not understanding *Which is more accurate, the hit-and-miss method or the improved Monte-Carlo method?* http://www-stat.stanford.edu/~susan/courses/s208/node14.html it is written that that the hit-and-miss has a higher variance but they showed (variance of improved Monte-Carlo) -...
  4. R

    Calibrating time-series simulations / backtests

    Suppose I have a time-series data generating process that I am trying to simulate. The simulations are controlled by 2 discrete variables: −3<= A<=3 and 0<= B<= 10. When backtesting, the simulations perform reasonably well, but I'd like the find the optimal values of A and B for calibration. I...
  5. R

    robustness-analysis of one-factor anova in R with negative-binomial distributed data

    Hello everyone, I'd like to examine the robustness of the Anova, given that the dependent variable is not distributed normally, but negative binomial. Therefore, I use the following code: pvalue = rep(NA, 100000) n = c(352, 198, 170) group = rep(1:3, n) for (i in...
  6. Y

    Population genetics: prediction of allele frequency distribution

    Is there a software or a R package that does a simulation of spatial distribution of alleles? I'm interested in how a distribution of alleles of functional loci is shaped by a pattern of environmental variables, such as temperatures and water quality. I have data on geographical patterns of...
  7. E

    Capture sums, not means, from individual iterations in a Monte Carlo simulation

    I am having difficulty setting up what should be a fairly straightforward application of the Monte Carlo Simulation function in SPSS 21. I have a dataset that includes hospitalization costs for a specific patient population. I set up a simulation that randomly selects a subset of cases based on...
  8. C

    Difference between MCMCsamp and sim

    Trying to get confidence intervals on a fixed effect in a mixed model fitted with the lmer function in package lme4 in R. I can get distributions of beta using "mcmcsamp" function and estimate a confidence interval from that, but I can also do it using "sim" in the package arm. While they both...
  9. S

    Simulation of unlikely events over random binary variables knowing their probability

    Hi, I have n binary variables all having the same probability p of flipping. Probability is low, so I wouldn't want to go through generating a random number for every one of them in order to flip their value. I know that the expected number of flips for the n variables is m = n*p. I could use...
  10. M

    Create loop for Monte Carlo Simulation

    Hi I have some trouble writing out a monte carlo simulation properly. I assign variables for the process before the steps. The first step is assigning variable j = j + 1 Second step i draw three random numbers from a U(0,1) dist. u1, u2 and u3. Third step is a long if formula. It...
  11. trinker

    Mic Check my simulation

    I'm not a statistician but like to pretend. I help a friend write simulations in R but don't really do the math end. Here's a small baby attempt at a simulation to answer Noetsi's question of how using a single Likert item vs an interval scale affects the estimates and slopes. Please give...
  12. I

    Comparison of the power of the tests: Parametric test versus Non-parametric test

    How can one compare using a simple experimentation or simulation whether a parametric test (e.g. t-test) is more powerful than its non-parametric counterpart (Wilcoxon signed rank test)? I understand that statistical power is defined as the probability of rejecting the null hypothesis when it...
  13. N

    simulation for probability

    I'm a brand new R user, and I have what is probably a very easy question. I ran a simulation to figure out a probability question. I'll show the code below, but I was wondering if anybody could tell me a more efficient way to do what I've done. The basic question is "If the correlation...
  14. B

    Multivariate analysis with dependent variables and replicates

    Dear All, I have been stuck in this issue for 2nd day now. I have a dataset of 13 depended variables (consequitive (not repeated!) measurment ("profiles" from one batch of product) and there are 3 batches (replicates) and within each batch there are 10 containers. So I am dealing with...
  15. C

    Estimating parameters of simulated Normal Data sets

    Dear Sir/Madam, I am doing a simulation study. For my study, I need to simulate 10,000 data sets from standard normal distribution(each with 100 observations) and need to estimate the mean and standard deviation parameters of all 10,000 data sets. I used replicate function to generate...
  16. T

    Generate random variate: What does this symbol mean?

    Hi. I'm reading a book about how to simulate random variate (from some distribution). But, when i look at the algorithm there, is has a leftarrow symbol, which i'm not sure what does it mean. I try googling but most of the results only state the LaTeX code for such symbol without further...
  17. C

    Simulation with Dichotomous Random Variables in R

    Hi, I am a bit new to R (I've used Stata before), but I am trying to figure out how to do a simulation in which I want dichotomous random variables whose expectation has a form like that of the distribution function of a logistic random variable. So far, I've decided to use runif, and I...
  18. P

    [WINGEN] - Data generation with IRT

    Hello everybody, I have a simulation study and I try to generate irt data with a program called WINGEN. I want to generate dichotomously scored, normal distributed and unidimensional data. And I my number of examinees are 10000, number of items 40 and my irt model is 2PLM. WINGEN asks me...
  19. P

    Data generation study with irt

    Hello everybody, I have a simulation study and I try to generate irt data with a program called WINGEN. I want to generate dichotomously scored, normal distributed and unidimensional data. And I my number of examinees are 10000, number of items 40 and my irt model is 2PLM. WINGEN asks me...
  20. A

    simulating psychology experiments, some questions :)

    Dear all, I hope you can point me in the right direction regarding two issues I am having with simulating experiments (1: regarding the legality of my assumption of different from chance, 2: regarding whether my simulation is valid at all). We conducted a study (I have attached a poster we...