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

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23 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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32 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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15 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
41 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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2answers
72 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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1answer
27 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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19 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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19 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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18 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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9 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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24 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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12 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
16 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 ...
3
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1answer
48 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
27 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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27 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
30 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
34 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
41 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
26 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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0answers
19 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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17 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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15 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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36 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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14 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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36 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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9 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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40 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 ...
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67 views

Kruskal Wallis: Effect size

I analyse 4 algorithms and 3 sets of metrics for each algorithm in which I apply the non-parametric Kruskal-Wallis test for each metric to detect any differences in performance between these ...
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0answers
17 views

repeated non-parametric Anova with a normal covariate options, best approach?

I'm looking for input on the best approach to a problem. I have data where each person experienced three conditions during a testing session (different priming stimuli for a memory test). There was ...
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27 views

upper bound for expected maximum of difference of two kernel-Estimations

I'm searching for an upper bound for a function like $$ E\left[ \max_{x \in R} \left( \frac{ \sum_{i=1}^n K(\frac{x-X_i}{f(x,X_1, \dots X_n)}) \cdot Y_i } { \sum_{i=1}^n ...
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39 views

Z Score for Non Normal Data [duplicate]

I am looking for some direction to see if there is an equivalent metric to a z score that could be used to quickly identify individual values in a non-normal distribution that are not likely to occur ...
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30 views

Non parametric test for ANOVA and coefficient of variation

Which is equivalent non parametric test for one way ANOVA ? Is quartile coefficient of dispersion for non parametric test equivalent to coefficient of variation (COV)? Among them which measures are ...
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25 views

How do I interpret significant Dunn's test results when the medians are the same?

Long time listener, first time caller... So I am looking at data with five subgroups. Data is negatively skewed in the group as a whole and in all subgroups. Kruskal-Wallis tells me there is some ...
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20 views

Bayesian process with noise?

Does anyone know of any research considering Dirichlet processes (or other Bayesian nonparametric models), where sample points have a known gaussian noise attached to their input? I.e. I have a set ...
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0answers
78 views

Are all models useless? Is any exact model possible — or useful?

This question has been festering in my mind for over a month. The February 2015 issue of Amstat News contains an article by Berkeley Professor Mark van der Laan that scolds people for using inexact ...
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44 views

Non parametric test/ANOVA/Parametric test?

My study design is a pre-post test measurements with a control group. My study design is Creatine Kinase being measured before and after exercise, and my subjects are divided into two groups; either a ...
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13 views

False discovery rate from non-parametric tests with small n

I have a bunch of paired readings of bacterial abundance, sampled from two different places in the same patient and divided by total bacterial cells found in each location. Thousands of species were ...
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25 views

Non-parametric test for repeated measures that are not independent

Seacucumbers were counted at the same 63 survey sites in three successive years (3 x 63 = 189 surveys in total). The distribution of counts per site are non-normal for each year. (Some sites have ...
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42 views

Comparing means between two groups if dependent variable is a percentage

I have data on recovery rates from several hospitals across the country. The recovery rates are in percentages. I want to compare the mean recovery rate between two groups of hospitals, one that uses ...
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10 views

creating a 3D kernel regression fit from a pool of predictors

i have a ~1k data set that has one response column(z) and 4 hypothesized predictors(x1-x4). i wish to create a 3D plot of the response surface, for example z ~ x1+x1 or z~x2+x4 i know that i need ...
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10 views

how to transform non-normal data for downstream statistical analyses [duplicate]

I have a dataset that look at the effect on photosynthesis and respiration. When i checked to see if the data looks normal or not, i find that for both the variables the distributio is non-normal. In ...
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2answers
87 views

Comparing frequency distributions

Quick rundown of my data: I have depth measurements from fish with implanted transmitters from two sites (reference and hypoxic) and two seasons (spring and summer). All data is in an Excel ...
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2answers
155 views

Why is Pearson parametric and Spearman non-parametric

Apparently Pearson's correlation coefficient is parametric and Spearman's rho is non-parametric. I'm having trouble understanding this. As I understand it Pearson is computed as $$ r_{xy} = ...
0
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1answer
88 views

Dunn.test in R: are adjusted p-values corrected for number of comparisons?

I've performed a post-hoc Dunn's test with Sidak adjustment using the dunn.test code for R. There are three groups in my comparison and I understand from the R help files that the lower number in the ...
3
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1answer
71 views

Find test statistic for sign test

I'm investigating if people are walking more than they bicycle. I have $n = 55$. $30$ of them are walking more and $25$ are bicycling more. I need to 1) find the test statistic for the sign test ...
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2 views

Comparing change in lateral root densities between treatments for different genotypes

I have been growing 4 genotypes of the same plant and been recording their lateral root density under both control conditions and a salt treatment. I have calculated the decrease in lateral root ...
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62 views

How many people initially had apples?

Story problem: Assume 10 apples are distributed across $X$ unknown people, where each person has at least one apple. For each apple a biased coin is flipped to see if that apple should be kept or ...
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35 views

Kruskal-Wallis post hoc comparisons different results in different software used

I'm having some trouble analyzing my data because when I use StatSoft Statistica and run a Kruskal-Wallis, I get one set of values for multiple comparisons, but when the same analysis is run in XLSTAT ...