Procedures that rely on relatively few assumptions about underlying probability distributions.

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Data analysis method for Tree selection

I need to select the best tree accession out of 350 vegetative propagated tree accessions. First I need to select straightness. Then I need to select for branching from above selected accessions. ...
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13 views

Can quantile regression be used to pool multiply imputed count data?

I am using the mice package in R to impute missing data in small study. The study investigates the effect of a behavioral intervention on the frequency of a particular behavior, i.e., count data that ...
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14 views

Data analysis method for tree selection

I consider 3 qualities of tree varieties; I call them $X,Y,Z$. I first select trees for $X$ character. After that selection will be done for $Y$, with use of trees which are selected for $X$. Finally ...
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40 views

How to test for a correlation between two variables, if the linearity assumption is violated?

I have two variables that show no linear relationship. It's not even monotonic. Does this mean that the variables are independent of each other? Can I still run a non-parametric test? Or can I just ...
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25 views

Non-parametric test for pre vs post between groups and unequal group size

I have pre-post test ordinal level data (likert). Pre and post samples were from the same population, but there was unequal group sizes (less people completed post compared to pre). I have run a ...
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26 views

Studying the distribution of the p-value?

I have two data vectors $X=(X_1, X_2, \dots, X_n)$ and $Y=(Y_1, Y_2, \dots, Y_m)$ where $X_i \overset{iid}{\sim} P$ and $Y_i \overset{iid}{\sim} Q$, and I am performing a two-sample test (i.e KS test ...
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1answer
28 views

Pairwise non-parametric test for small sample sizes

I was asked to check a small dataset (3 replicates for 5 treatments, each) for significant outcome differences. I give an example: The variance within replicates in the data cannot be assumed ...
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24 views

Limitations to generalized additive model (GAM)

I don't quite understand the generalized additive model behind the GAM package in R. It seems quite powerful with the ability to easily find complex relationships and confidence intervals for these as ...
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1answer
21 views

non-parametric analysis

I have faced a problem with my data which have different disrtibution. I have some data that are scaled one so possible to do ordinary parametric analysis on them (ANOVA, Correlation, ...) and series ...
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13 views

Multiple comparison of non-normal, heteroscedastic data. What test should I use?

I have a set of brain pathology data. These were obtained by counting certain parameters in the brain. Due to availability of human brains, the amount of cases vary a lot across the different groups ...
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13 views

What is the correct measure of significance to use on a small non-normal mixed data set?

I'm trying to run statistics on a small data set that does not have a normal distribution (possibly due to size of sample). I'm trying to work out if the sample group has any effect on the result ...
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13 views

Is there a stats test to compare the evenness of species in two different sites?

I'm writing up some ecological fieldwork and I have presence/absence data for 50 species in 30 quadrats (samples) for each site. A few species were found in most of the samples (say 28 or 29) while ...
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2answers
63 views

Does Spearman's Rank Correlation Imply Periodicity?

I have collected data from an online survey that asked people to 'rate' a corpus of music track excerpts with 8 emotional adjectives such as 'happy', 'sad', 'angry', etc. They could only select one ...
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25 views

What is the equation for multivariate kernel density estimation techniques?

I was reading about non-parametric kernel density estimation. http://goo.gl/UcIjmh For uni-variate where D = 1, we can write like** For Multivariate Kernel density estimation (KDE), more ...
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1answer
235 views

Examples of Non-Linear Time Series?

Does anyone have an example of real world (ideally multivariate) time-series data that depends on its past in a non-linear, but additive way? I understand that there are several examples of ...
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1answer
22 views

Should the sample sizes be equal for non-parametric tests?

I randomized samples into two experiments and I ended up with about 190 samples in one group and 80 in the other. The distributions of the two samples are not normal and I want to use Wilcoxon test to ...
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2answers
57 views

Understanding Big/Little $O_p$/$o_p$ Notation for Estimators

I am reading a Text about Single Index Models (SIM), where a SIM is defined as $E[Y|X=x] = G(X' \beta)$, with $G$ and $\beta$ unknown. After proposing an estimator for the function $G$, the ...
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34 views

Transformation of variables to fulfill normality assumption before GAM

We are running a GAM with highly skewed (and positive data) both in the dependent and in the independent variables. We have chosen to transform both the dependent variable (cubic root transformation) ...
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30 views

Test that a sample is non-randomly drawn from a population with arbitrary distribution

I have a dataset in which there are about 500 measurements for a particular scoring metric. The data are normalized so that the mean is 0 and the standard deviation is 1, but the distribution is ...
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1answer
66 views

KS Test and Wilcoxon Rank Sum Test, large differences in p values

I am relatively new to non-parametric tests. I wrote the following R code to test 2 sample tests using the KS test and the Wilcoxon Rank Sum test. Drawing 2 samples of various sizes from unit Normal ...
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27 views

How to apply non-parametric methods to panel data? “The Elite Illusion: Achievment Effects at Boston and New York Exam Schools”

I'm studying this paper The Elite Illusion: Achievment Effects at Boston and New York Exam Schools. There the authors use a fuzzy regression discontinuity design experiment to assess the ATE of going ...
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45 views

Which statistical test to use on mean data?

I have sets of data from two sample A and B. the data in sample A and B are the average mean of the population sample. Examle, sample A has list of data. each data in he sample is a an average value ...
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37 views

Skewed data, unequal n - advice?

This is the first time I have dealt with non-normal data (lucky me!), and I have come to a bit of a road block as to what tests to run. Experiment: Investigate whether false feedback affects ...
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22 views

German tank variant: estimate resolution of camera given cropped photo sizes

Make whatever assumptions you like, but I like the flavor of nonparametric techniques. I have a list of the $x_i$ by $y_i$ resolutions of a number of photos, all cropped from photos taken at the same ...
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3answers
74 views

Using KS test to evaluate differences

There are two different empirical CDFs which I have and I would like to evaluate how different they are. The place at which I started was Kolmogorov-Smirnov test - the result in my case looks like ...
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92 views

Looking for a robust, distribution-free/nonparametric distance between multivariate samples

There are many distance functions for distributions out there, but I'm having a hard time wading through them all to find one that is "distribution-free", or "nonparametric", by which I mean only ...
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37 views

How can I find out the needed sample size

I'm going to study if medical reconciliation diminishes the amount of inappropriate medications amongst elderly people in a small part of Sweden. I will count the number of inappropriate medications ...
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20 views

What to display for differences of medians of discrete variables?

I am using the Mann-Withney U test to compare two samples of count data. In several situations, I find that there is a significant difference between the populations, but when I estimate the CI for ...
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25 views

What method is appropriate? - analysing patterns of attacks by region

I am currently working on a project using a dataset on global terrorist attacks. For each attack there are details on the type of attack which has 7 levels (e.g. bombing, assasination etc.), the ...
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22 views

How to approach a between-subject comparison where only within-subject comparison is valid?

This is a rather odd situation, I'm guessing. I am interested in investigating a between-subjects factor and a within-subjects factor. However, the variable of interest is not one that can be validly ...
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11 views

Additive best-fit parametric kernel estimation?

I'm thinking of a process similar to kernel density estimation, but using fitted kernels. The process would be something like this: Create a histogram $H_1(x)$ with infinitesimal bins (such that the ...
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13 views

comparison of Akritas et al's & McKean et al's nonparametric ANCOVA models & script of Akritas' model

I'm currently analysing the results of a pretest-posttest experiment with a categorical independent variable with four levels (three treatment groups and a control group) and a continuous dependent ...
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25 views

How to find the distribution of data? Can the distribution be sum of multiple distributions?

I need to find the distribution of the demand data to generate the demand. I tried to fit distribution using tools in excel and python. But for all the distribution, p-value was high (in simple terms ...
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14 views

Mean Shift Kernel Choice

In a recent paper by Yen-Chi Chen et. al. "Enhanced Mode Clustering", a nice result on the consistency of the estimator of the mode from the mean shift is given. The conditions for this consistency ...
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1answer
23 views

Comparison of multiple independent data points (of variable number) for each subject within a group

I'm looking for a test to statistically compare different groups that have multiple data points for each subject within a group. Without getting into too much detail about my specific measurements, an ...
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1answer
61 views

Rank versus Box-Cox transformation

I'm attempting to assess the relationship between two quantitative variables, but the DV is highly skewed (and so are the residuals). I work among biologists who tend to favor non-parametric ...
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1answer
34 views

2 factorial experiment (2 by 3). DV is NOT normally distributed

I just conducted an 2 factorial experiment that has 6 conditions (2 by 3). Specifically, my design is: IV1 = prior positive information (positive in A domain vs. control vs. positive in B domain) IV2 ...
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30 views

Estimate density dependent on another variable

I have an (unknown) random function $y=f(x)$, i.e. for each value of $x \in [0,1]$ it is a random variable with some distribution. Also I can sample this function, and got values of $y$ for many ...
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1answer
37 views

Which test? Chi-square, non-parametric or Poisson Regression..? What species is the most frequently observed

I'm reposting my question based on previous comments received. The problem: 10 x 100m sections of shoreline have been sampled to determine if one species is the most frequently observed species ...
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1answer
39 views

Are two variables that are dependent also correlated? / Can two dependent variables not be correlated? [duplicate]

I cannot find the answer to my question anywhere, I hope someone can help. I did a Chi-Square test with several variables to see if they were dependent or independent. The result showed that they ...
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2answers
51 views

Non-parametric tests in big data scenario

Suppose I have two populations A and B , with sizes $n_1$ and $n_2$ respectively, where both $n_1$ and $n_2$ are large (say, above 500). I want to test that the values $x_1, \dots, x_{n_1}$ of A ...
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1answer
28 views

How to sample from a non-parametric density estimate?

I have a kernel based non-parametric distribution, let's assume it's a Normal kernel, but the variance of each component is different. How do I sample from this density? If all the components had the ...
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23 views

Non-parametric variogram estimators

I'm working with overdispersed, count spatial data. The goal is to look specifically at spatial dependence patterns. I'm trying to fit variogram models to empirical variograms, however the only ...
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23 views

Interpreting the Cowan Generalized Sign Test formula

I'm working on a finance project where I have to calculate a number of statistics related to abnormal returns surrounding an event. One of the tests I'm doing is the Cowan Generalized Sign Test, ...
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17 views

What is the difference between DEA and SFA in terms of data used?

I read that Data Envelopment Analysis (DEA) is non-parametric approach while Stochastic Frontier Analysis (SFA) is parametric approach. Does it make any difference using one of the approaches ...
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40 views

Endogenous interactions in nonparametric instrumental variables

I'm interested in estimating a model along the lines of $$ pr(y==1) = g^{-1}\left(f(x_1,x_2)+X'\beta\right)+\epsilon $$ where $g$ is logit and $f$ is some smooth function. I'm using GAM's in ...
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20 views

How can I express $D_{m,n}$ as a distribution free statistic in terms of $d_l$

Consider 2-sample problem with m and n observations from the mutually independent, absolutely continuous populations $F_X$ and $F_Y$, respectively, define 2-sided kolmogorov-smirnov statistics ...
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39 views

Is this how a Bayesian bootstrap works?

I am a bit new to the whole nonparametric and Bayesian idea, so tell me if this is correct: to estimate, say, the mean of a dataset's population we do the following: We define a function $f(x)$ that ...
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12 views

test ranking differences across three groups

I have three groups A, B, C, with participant ns of 20, 89, and 165. Each participant ranked her or his concern with 14 items (potential impediments to success). Scale was 0-1-2-3, 3 = most concern. ...
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42 views

Confused about whether to use t-tests or ANCOVA or ANOVA

I am investing whether vitamin C supplementation can attenuate creatine kinase increases after a strenuous workout. My participants are divided into two groups, VitC group and a Control (no ...