bootstrap

  1. A

    Bootstrapping with sample(), what should the size of your sub-sample be?

    Hi I am currently bootstrapping my sample, x, using the sample function. sample(x, size = n, replace = T) My question is how do you know what size should be? Is there a standard procedure in determining the value of size?
  2. B

    How to continue raw data for Forcasting ~ Holts-Winter

    Hi All, I am new to this forum and i am in need of help regarding the Holt's Winter Method. I've managed to build a forecasting model in excel using the Damped method which works very well. But due to my lack of experience, I am confused on how to continue the raw data as the forecasting...
  3. T

    Bootstrapping and Independent T Tests

    Dear all, My question is whether it is appropriate to use Independent T Tests on distributions generated through bootstrapping. To be more specific: I used bootstrapping to generate 1000 subsamples for each of two observed distributions from different samples. I then used an SPSS macro to...
  4. Y

    Unbalanced designs in PERMANOVA and Resampling Methods

    Dear all, I am a new member here, working mainly in Ecology. I hope this is the right section to ask my question. I am dealing with unbalanced designs (I am comparing groups with different sample sizes) in PERMANOVA (Permutational Multivariate Analysis of Variance). The PERMANOVA runs...
  5. Y

    Unbalanced designs in PERMANOVA and Resampling Methods

    Dear all, I am a new member and I have to say I am not sure if this is the right section for my question (I am working in ecology). I am dealing with unbalanced designs (I am comparing groups with different sample sizes) in PERMANOVA (Permutational Multivariate Analysis of Variance). The...
  6. rogojel

    Bootstrap and hypothesis test

    Hi, I have to decide whether two groups have the same variance or not. My sample size is less then impressive, 13 data points per group. I ran Bartletts test and got a p-value of 0.09 - but I suspected that the relatively high value might be due to the small sample size. So, I ran a...
  7. M

    Bootstrapping 0.632+ AUC with fixed test sets

    Hi, I want to compare different binary classifiers in terms of their AUC values on test sets. I have data over one year with about 2000 observations each month. Now I would like to use the data in each of the last three months as separate test sets while using the months prior to a...
  8. L

    The bootstrap method for medical modelling

    I am part of a team creating a model for paediatric hospitalised patients and would appreciate some help. We are looking to produce an accurate model for weight estimation, using input variables of gender, age and mid-upper arm circumference. This would be helpful as some children arrive in...
  9. P

    How to Fit polynomial regression by bootstrap and establishing IC of each parameters

    #Hi everybody and excuse me for my bad english for this request on R. #here parameter of an hypothetical interval : x=c(60,59,55,49,43,38,33,28,24,20,17,15,12,10,8,6,5) y=c(59,55,49,43,38,33,28,24,20,17,15,12,10,8,6,5,4) #I adjusted it by a polynomial regression degree 3 (not the best...
  10. S

    Bootstrap procedure to test difference between correlation coefficients

    Hi everyone, I have two correlation coefficients (r1 and r2), obtained within the same sample (20 subjects). My aim is to test it they are significantly different. r1 is the correlation between a neurophysiological parameter and a behavioural parameter in condition A; r2 is the correlation...
  11. T

    How to merge two data sets with varying date intervals?

    I'm sure this problem isn't unique. I have two sets of data, both $ values and I want to add them together and plot them on a chart. The problem is that one data set is quarterly and the other is daily but I want to display the resulting set (the addition of the two data sets) in weekly or...
  12. A

    Bootstrap strange estimate

    Hello everyone, I'm a statistical novice, I would like your help. I'm analyzing non-normally distributed variables. To develop the confidence interval I preferred to use non-parametric method: bootstrap. Unfortunately I get output biased estimates and standard errors high, even though I used a...
  13. S

    Bootstrapping code help needed in r??

    Hello friends. So I am ready to jump off a building because I cannot figure out this code for my LIFE. Everytime I run it, I get the standard error of 0 (bias=0 too) so obviously I'm doing something wrong because it's using the same sample when I want 1000 iterations. I want the AIC of the...
  14. P

    Inaccuracy of Non-Parametric Bootstrap for great sample sizes in Excel-VBA

    My aim is to evaluate the performance of parametric and non-parametric Bootstrap under specific circumstances; and particularly their ability to capture the population mean within their produced confidence intervals -from now and on when talking about "coverage" I mean the ability of the...
  15. R

    How can I compare two bootstrap-generated distributions?

    Hi everyone, I've generated variability around my single endpoint value with the bootstrap method (endpoint = intrinsic growth rate "r" ). I've done this for my control and my treatments. Now, how can I compare these distribution so that I can tell if this endpoint is statistically...
  16. S

    bootstap for cluster sample

    I'm trying to write the SPSS syntax that will do bootstrapping on a one-stage cluster sample--that is, one where a random sample of clusters is selected, then all elements within the selected clusters are analyzed. Any help would be appreciated.
  17. L

    Mediation, Bootstrapping and Sample Size

    I'm new to statistics overall, and even newer to mediation but I'm attempting to analyze data using Process for SPSS. Before anything else, do I need a specific minimum sample size and how do I determine this? Does bootstrapping take care of this, and then, how many bootstrapping samples do I...
  18. E

    Logistic regression, sample sizes and bootstraping

    Hello, this is my first post. I currently I'm working in my phD in a multivariate logistic model but I have a problem regarding the sample size of my observations: -The "success" (1) event group has a sample size of 249 distinct observations - The "non success" (0) event group has a sample size...
  19. U

    Testing heteroskedasticity in a bootstrapped quantile regression

    Hi, I am currently using stata to perform some regressions, and need help on how to perform specific tests on bootstrapped quantile regressions. I have a dataset with 31variables, most of which are dummies, and 1600 obs. I am looking to perform quantile regressions as the distribution is...
  20. amsavage

    bootstrap estimates with summary data

    I feel like this may be a silly question, but pride aside: If you only have access to summary data (cov matrix, means and SD) can you still generate bootstrap estimates in AMOS? I think the answer is likely 'not without raw data' but I would like to see if any other ideas exist out there on...