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

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Non-parametric test for 3 paired samples that are not independant

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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19 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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2 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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17 views

Non parametric or parametric test [closed]

I have a data of some athletes' sprint times. They are two groups one with less than 2 years experience and on with 5-8 years experience. Well i need to establish if there was a difference between the ...
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22 views

nonparametric estimation to similar shapes with different mean and variance [closed]

I have several counting datasets. The distributions' shapes are similar, but their mean and variance (scale) are quite different. Is there any method to estimate these datasets? What I need is a ...
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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
76 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
123 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} = ...
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1answer
29 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 ...
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1answer
57 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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61 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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20 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 ...
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30 views

Curse of dimensionality [closed]

The thread curse of dimensionality & nonparametric techniques talks about the curse of dimensionality in nonparametric technique. Can it be a problem even for parametric technique?
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6 views

Data set distribution by state compared to US pop distribution by state

thanks in advance for your help. -I have a survey data set in which people reported which US State they are from. -I have the proportions of the entire data set comprised of people from each state, ...
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1answer
34 views

Is dunn.test a suitable alternative to kruskalmc in pgirmess package?

I'm trying to run the krushkalmc method after running kruskal.test as part of my analysis with the Kruskal-Wallis rank sum test. I have data with a small sample size that also does not have a normal ...
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1answer
56 views

Probability that randomly chosen value from one distribution is greater than randomly chosen value from another distribution

Say I have $n$ values sampled from two distributions, $A$ and $B$ . That is, I have a sample $A_1, A_2, \dots, A_n$ and a sample $B_1, B_2, \dots, B_n$. How would I go about finding ...
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7 views

Correlation between ordinal and dichotomous variable with repeated measurements

I ask say 50 people to rate 10 statements whether they are true of false (dichotomous answer). The 10 statements were rated concerning the occurrence of specific cues (such as details or emotional ...
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1answer
51 views

Convergence rate: $E\|\hat f - f\|^2 = O(\psi_n)$ vs $\|\hat f - f\| = O_p(\psi_n^{1/2})$

I have seen two types of results on convergence rates for some estimator $\hat f$: $E\|\hat f - f\|^2 = O(\psi_n)$ and $\|\hat f - f\| = O_p(\sqrt{\psi_n})$. The first result seems to be stronger, ...
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1answer
62 views

Excess Bunching - Bunching Estimator (Saez 2010)

Saez (2010) defines excess bunching at the kink as the area under the density in the dominated region: $$ B = \int^{z^*+d z^*}_{z^*} h(z)dz \approx h(z^*)dz^* $$ where income $z$ is distributed ...
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21 views

Confidence intervals for a curve with bootstrapping

I am estimating y= az + f(x) in a semi-parametric way. I want to compute the standard error for the estimated coefficient for a ...
2
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1answer
64 views

How can I measure difference between non-parametric data with many zeros?

I'm comparing two groups of students by their course activity and I'm struggling a little to determine the best way to test for significant difference. The data is non-normal, and very prevalent with ...
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21 views

Correlation to use for non-scale data( counts)

In our college we run some extra non-required sessions that we hope help the students. To decide whether they help, I wanted to correlate the number of sessions attended with the cumulative gpa of ...
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13 views

What is the complexity of locally linear regression on many grid points?

Say I have $n$ data points and I want to estimate $f(x)$ at $m$ locations, where both $n$ and $m$ are large. Are there any common algorithms for computing locally linear regression estimates at all ...
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1answer
32 views

Choosing a line/plane to separate two classes of binned data

In high energy physics I know it is common task to find the best separation point between two classes of data, usually signal and noise. This separation point is usually determined by first binning ...
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2answers
128 views

Inverted nonparametric rank test

I have two related samples, for which I want to prove they are not significantly different (normally you would test for the opposite, i.e. samples are significantly different). If I use Wilcoxon ...
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1answer
41 views

Critical value for Wilcoxon one-sample signed-rank test in R

I am trying to find the critical value for the Wilcoxon one-sample signed-rank test. Currently, I can find the value using tables. I looked at qwilcox() in R, but ...
2
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1answer
104 views

Local polynomial regression: Why does the variance increase monotonically in the degree?

How can I show that the variance of local polynomial regression is increasing with the degree of the polynomial (Exercise 6.3 in Elements of Statistical Learning, second edition)? This question has ...
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10 views

Is there a blocked replicate test like Friedman Test, but for data across different populations?

I'm working on my analysis for a thesis project. I have two years of data, where I measured number of bats approaching boxes. The boxes are set into replicates, with each replicate having 5 treatment ...
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6 views

Variance decomposition of fixed factors and stochsticity

I am running a model sensitivity analysis of a model that yield results based on several (fixed) input parameters and some randomness (stochasticity). So in order to get the sensitivity of the model's ...
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25 views

Non parametric version of Hotelling's $T^2$

Is there a non parametric version for Hotelling's $T^2$ test? Namely, the one group test for location (not the two group).
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1answer
41 views

Using ANCOVA when the covariate is not normally distributed

I have conducted a repeated-measures ANOVA, but a reviewer suspects that the observed main effect of condition are due to a the difference between hit rates of two conditions (one of them is ...
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29 views

Example of parametric and non-parametric method

I have not understood this example from wikipedia. Suppose we have a sample of 99 test scores with a mean of 100 and a standard deviation of 1. If we assume all 99 test scores are random samples ...
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1answer
55 views

Non-robustness of parametric statistics

Why is parametric test considered to be non-robust ? Or, why is parametric test not considered to be robust?
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1answer
31 views

Parameters in a non-parametric model

I have not understood this Wikipedia statement: The difference between parametric model and non-parametric model is that the former has a fixed number of parameters, while the latter grows the ...
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1answer
58 views

Can one do GLM with LOESS transformed variables

I have binary valued classification variables, and predictors that are not really performing great in GLM with probit/logit model. Some of the predictors are also correlated with each other. I am ...
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56 views

Where is the maximum bias and variance in a histogram as non-parametric density estimator?

I am a little bit confused about bias and variance of non-parametric density estimators and hope you can help me. Assuming a constant bandwidth and sample size, I am wondering at which points of the ...
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28 views

Confidence intervals for median from Wilcoxon signed rank statistic

We are given the sample $X_1, ..., X_n$ from a common distribution with median $\mu$. Using Wilcoxon's signed rank statistic, how can I construct a confidence interval in terms of the order statistics ...
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45 views

non normal data - bootstrap pearson r or kendall tau?

This may be a follow up on these questions: Pearson's or Spearman's correlation with non-normal data How robust is Pearson's correlation coefficient to violations of normality? ...
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1answer
19 views

Test to determine correlation between organism size and concentration?

I have a gamma distribution. I am looking to determine if higher concentrations of a toxin are correlated to larger organism size. I think a non-parametric test would be best, but I'm not sure which ...
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20 views

Kolmogorov-Smirnov test: horizontal variant?

The Kolmogorov Smirnov test is based on the maximum vertical distance between the ECDFs of two provided samples. Is there a variant that checks the maximum horizontal distance?
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20 views

Nonparametric alternatives to 1-way anova?

Are there non-parametric alternatives to one-way analysis of variance? Ideally, I am looking for something that is easy to understand and can be done in SPSS.
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26 views

Can I use a Spearman Rank-Order Correlation test to check the impact of potential confounders in my data?

I have a relatively basic statistics knowledge, so I apologise in advance if this question doesn't fully make sense or if I'm totally off-base with how I'm trying to analyse it. I've got a project ...
2
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1answer
50 views

What is “Targeted Maximum Likelihood Expectation”?

I'm trying to understand some papers by Mark van der Laan. He's a theoretical statistician at Berkeley working on problems overlap significantly with machine learning. One problem for me (besides ...
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23 views

Estimate E[x|A,B]: alternatives to bucketing for non-parametric estimation

I have a set of products. I would like to estimate Expected Value of items sold of the products wrt product price and age of the purchaser. One alternative is to assume a distribution and fit it. ...
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36 views

Non-Parametric ANOVA: Repeated Measures with Replication

I'm struggling to find out which ANOVA test to use when you have a non-normal data set with repeated measures AND replication. I'm doing my data analysis in R and the friedman.test() method says it ...
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1answer
41 views

Chi-Square test: one-sided implementation?

I need to compare two samples and I would like to know if the distribution of the first stochastically dominates that of the second one. I'm not sure whether with the Chi-Square test I can verify ...
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1answer
40 views

Density Function Estimation

Given a sample of $n$ observations, which are assumed to be $i.i.d.$ and generated from a continuous probability law. Consider the question of estimating the density function $f(x)$. There are two ...
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What's the best way to demonstrate differences in these means/totals?

With some co-authors, I coded 200 video game reviews based on whether they mentioned any of nine different game elements. We now have the total number of times that each game element showed up in ...
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23 views

hypothesis test for discrete disributions

I am interested in the number of instances of feature $F$ among the members of two populations, $A_1$ and $A_2$. e.g. $F$ is a some special genetic element that may occur several times within a ...