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

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In practice, how is the penalisation matrix for splines, created by smoothCon (package mgcv), specified?

Evaluating a smooth object with smoothCon provides, besides several other things, the ordinary "untouched" spline bases ...
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24 views

small n: some variables are normally distributed some are not

We performed a biomechanical study, comparing an intact state to 5 different deficiency states on the same knee cadaver specimen. This was conducted on a very small sample size (n=8). My problem is, ...
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12 views

Problems with calculation of numerical identification w.r.t. ANOVA smooth for large scale matrices

Suppose we have two (centered) Spline-matrices $\boldsymbol{B_1}$, $\boldsymbol{B_1}$. Then $\boldsymbol{X_1} = [\boldsymbol{B_1},\boldsymbol{B_2}]$ contrains lower order smooths and ...
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10 views

Multiple comparisons on nested subsets of data for a non-parametric test

My problem: I'm using data sets where some are nested in a non-parametric test that expects independent data sets. How can I correct for that in a way that is reasonable? Or even better: What would ...
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1answer
16 views

Effect of sample decimal points on power in rank-based tests

I perform different rank-based non-parametric tests (Friedman and Nemenyi) post-hoc and noticed that the decimal places of the samples have a strong effect on their power. Please consider the ...
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17 views

Stores and ordered rank of products

I have data about popularity of some products in some stores. For each of the stores I have only a ordered rank of best-selling products in them. I need help how to find information about which ...
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2answers
116 views

Why am I getting inconsistent results from Wilcoxon signed rank test and Kruskal-Wallis test?

I am doing a study on 3 drugs, comparing response pre-post treatment. My objective is to know if these drugs are effective and which one is better. I used non parametric tests since the results ...
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13 views

How to calculate confidence interval for difference (or ratio) of two different time series?

I have two time series which are sampled at the exact same times. I would like to calculate a confidence interval either for the ratio between the two or the difference between the two. The values ...
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1answer
24 views

What R packages are available for nonparametric regression of two predictors?

I would like to fit a nonparametric regression model with two predictors. What R packages are available? I found 'loess' function in 'stats' package and 'gam' function in 'gam' package. Is there ...
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3answers
131 views

Should I use t-test on highly skewed and discrete data?

I have samples from a highly skewed dataset about users' participation (e.g.: number of posts), that have different sizes (but not less than 200) and I want to compare their mean. For that, I'm using ...
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13 views

Comparing transaction counts between samples

I have a treatment group and two control groups for customers and the count of their transactions: ...
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1answer
24 views

Which test to use for paired, nonparametric, categorical data?

We asked a group of subjects to tell us their preferences for a given procedure, of which there were 4 choices. We then provided them with educational material and asked them again of their ...
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13 views

Fast evaluation of univariate KDE?

I have a KDE obtained with a large sample ($n=10000$). Given that this is defined as the mean of the kernel evaluated at $n$ points, the evaluation of this kernel slows down my code (I need to ...
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10 views

Non-normal data (ceiling effect) and intraclass correlation

I am wondering if there is any way of doing an intraclass correlation, two-way, mixed, with non-normal data (in this case a ceiling effect)? Alternatively, what the interpretation (if any) would be? ...
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1answer
9 views

Is the Friedman Test Suitable For an Analysis of Pre/Post-Intervention Choices From Survey Data?

We sent out a survey to find if educational material about a type of surgery would potentially influence the decision of subjects. Prior to giving them this educational material we asked them ...
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1answer
655 views

Should I use t-test on highly skewed data ? Scientific proof, please?

I have samples from a highly skewed (looking like an exponential distribution) dataset about users' participation (e.g.: number of posts), that have different sizes (but not less than 200) and I want ...
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0answers
9 views

How to analyze data with unequal observations per cell?

I've got a very poorly designed study, and I need to find a way to analyze the data I've collected. Here's a description of the design: There are two within-subjects variables, one with four levels ...
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33 views

Repeated measure two-way ANOVA (non-parametric)

Non-parametric ANOVA – a hot topic that is unanswered. There are many questions on this topic online. However, they all seem to end in a debate and no definite answer or clear explanation (that I ...
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49 views

How exactly is the sum (or mean) centering constraint for splines (also w.r.t. gam from mgcv) done?

The data-generating-process is: $y = \text{sin}\Big(x+I(d=0)\Big) + \text{sin}\Big(x+4*I(d=1)\Big) + I(d=0)z^2 + 3I(d=1)z^2 + \mathbb{N}\left(0,1\right)$ Let $x,z$ be a sequence from $-4$ to $4$ of ...
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3answers
66 views

How do I compare sample means in this experimental-control group study?

I am hoping to compare the sample mean of an experimental group to the sample mean of three control groups. Here is some context for the study: The experimental group consists of ~60 persons with a ...
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16 views

Non parametric test for multivariate data

Please suggest a non parametric test that is analogous to the MANOVA. I have 7 nutrient intakes of men and women. How do I test if their intakes are equal?
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1answer
18 views

Sum of Squares Constraint Regularisation

Suppose I have a function $g_0\in L_2(\mathbb{R})$ such that we observe $(X_i,Y_i)$, $i=1,...,n$ such that $$ \begin{align*} Y_i & = g_0(X_i) + V_i \end{align*} $$ We wish to estimate $g_0$, ...
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1answer
63 views

Multiple comparisons in a non-parametric test

I am working with a data set that is non-parametric and has 12 treatments. I performed the Kruskal-Wallis test and got a significant $p$-value, and now I would like to conduct a multiple comparisons ...
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2answers
41 views

Which test do i choose to conduct on my Likert scale data?

I have been doing plenty of research into which test I should use on my Likert scale data and i am becoming more confused as there are so many people saying different things. I am currently doing my ...
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1answer
25 views

Approaches for extracting single-year age estimates from age-buckets

I'm trying to estimate a binary function of $Y$~$Bernouli(p_{i})$ where $p_{i}=f(age)$ where f is an unknown continuous function. There are obviously a lot of methods to try to reconstruct f (splines, ...
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45 views

How does the cubic spline basis exactly look like

By the definition (1) $S(x)=\begin{cases} S_0 = a_0x^3 + b_0x^2 + c_0x + d_0, & \text{if }t_0\le x\le t_1\\ .....\\ S_{k} = a_kx^3 + b_kx^2 + c_kx + d_k, & \text{if }t_{k-1}\le x\le ...
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18 views

How to analyse individual consistency from three non-normally distributed variables?

I would like to know if individuals were consistent across three different days. I measured the latency of individuals for a maximum of ten minutes. Many individuals had a latency of 0 and some ...
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0answers
10 views

Reliability Measure for Unequal Subjects between Raters?

I am comparing two medical imaging analysis techniques, and I would like to assess the inter- and intra-rater reliability for using each method. I am planning the study design, and would like help ...
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1answer
22 views

Is system identification and learning examples of parametric or nonparametric methods?

Difference between parametric and nonparametric statistical tests and What is the difference between distribution free statistics/methods and non-parametric statistics? is a good read for beginners. ...
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0answers
8 views

Identify significant deviations (gaps) of points in a 2-D distribution

Consider an $X_i$, $Y_i$ distribution of points in a 2D plane. How can one assess if a given region in this 2D plane has a significant lack of points when comparing with the rest through a ...
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1answer
33 views

Statistics Test for bivariate frequency table

First time user here! I have some troubles in finding some statistic method that would fit my purpose for testing bivariate frequency table. Below is a sample frequency table I have created with ...
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42 views

Nonparametric test for largely skewed count data

My research design looks as follows: an experimental game with 4 participants (human subjects), repeated for 20 rounds. During each round, participants are allowed to form bilateral coalitions which ...
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6answers
357 views

Dealing with non-normal distribution in “big” datasets, when do we throw out the CLT?

Apologies from the go as this question comes from an absolute newbie and will definitely not satisfy a lot of the detail required. Hence, your guidance in providing you the right information to allow ...
4
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1answer
64 views

Nonparametric ANOVA with interaction?

Is there any nonparametric version of ANOVA able to deal with multiple factors AND evaluate their interaction(s)? If the interactions are really impossible to evaluate, is there any generalization of ...
0
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1answer
37 views

Difference between skewed continuous variable and/ or ordinal variable by their binary group allocation

I need to select the most appropriate hypothesis test to answer: "whether there is any difference between variable 1 (ordinal) and/or variable 2 (continuous) by group (binary)". This is a randomised ...
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20 views

Kruskal-Wallis test for factorial design [duplicate]

Is it possible to use the Kruskal-Wallis test for two factors and their interaction (i.e., two way ANOVA: Y~a*b)? And which post-hoc test is possible to use after ...
2
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1answer
57 views

Absolute variable as dependent variable

I have the following model: $$ |X| = B_0 +B_1 \cdot y + B_2 \cdot z , $$ where $z$ and $y$ are normally distributed random variables, and $B_1$ and $B_2$ denote the coefficients. My dependent ...
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22 views

Is there an alternative to paired t-test two multilevel ordinal variables? (similar to McNemar test)

Suppose I have two variables that measure some form of severity of illness on identical ordinal scale; one measured before treatment and the other measured after the treatment. I want to test if ...
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1answer
74 views

What is the difference between a parametric test and non-parametric tests? [duplicate]

Please explain the difference between a parametric and a non-parametric test. Do all data mining techniques come under the non-parametric category?
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1answer
33 views

Bootstrap hypothesis testing with small sample sizes

I have 2 campaigns (a control and a test campaign), the data are like this: ...
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62 views

Testing specific categories after Fisher's exact test in 2 x k tables

I have two variables, one with 2 categories and one with 6 categories. To test, whether there is any relation between these variables, I performed Fisher's exact test, which gave a significant result. ...
4
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1answer
107 views

Computing inverse probability weights — conditional (multivariate) density estimation?

The general version: I need to estimate $f(A | X)$ where $A$ and $X$ are continuous and multivariate. I'd rather do it nonparametrically because I don't have a good functional form in mind and ...
0
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0answers
37 views

Best non-parametric test for continuous dependent variable and binary independent variables

I am struggling with the choice of which test would be appropriate for my data. My sample size is very small (n=16), thus I have chosen to perform a non-parametric test in order to prove my ...
2
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2answers
69 views

are “non-parametric” methods well-defined?

I have trouble understanding the delineation of "non-parametric" methods. It seems to me most non-parametric methods are parametric, just on a different space than the "standard ones". Graph-based ...
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0answers
29 views

Statistical test decision tree / reference card

I'm in need a reference card to help in deciding which statistical test to use depending on study design, variance, class size, groups, etc. Anything like this available?
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1answer
36 views

Ignore assumptions and still go ahead with a parametric test?

I have data which is not normally distrubuted (histogram doesnt show a bellshape data and normal plot shows a bit of a zig zag data going through line of best fit) but standard deviations are of ...
2
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1answer
54 views

Hypothesis testing for multiple choice quiz

I am trying to determine whether students perform better than chance on a quiz with $q$ multiple choice questions. Each question as 4 possible responses; one is correct and 3 are wrong. A correct ...
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16 views

Generalizing van Elteren to more than two treatments

I know about the following tests: Mantel-Haenszel for categorial stratified data Kruskal-Wallis for nonparametric ANOVA for more than two treatments Friedman for a repeated measures version of ...
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2answers
84 views

Non parametric measure of strength of association between a discrete and a continuous random variable

I'm throwing here the problem as I received it. I have two random variables. One of which is continuous (Y) and the other one which is discrete ordinal (X). I put below the plot I received together ...
2
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1answer
30 views

How to deal with non-normal heterocedastic data from a factorial experiment?

I ran an experiment with two factors each with two levels, 5 replicates each combination and one response variable. My data are non-normal and heterocedastic. Transformations didn't help. I ran a ...