Tagged Questions

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

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0
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0answers
32 views

Kernel Estimator [closed]

What is the behavior of the kernel estimator when a single observation moves to a very large value, that is $(X_i,Y_i)\to (X_i,Y_i\pm c)$ with $c\to \infty$ for a fixed $i$. and as one of the ...
4
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0answers
25 views

Rank deficient bootstrap resamples

Despite years of stat courses I'm afraid I may still not completely understand bootstrapping. My question here relates to nonparametric boostrapping of regression models. As i understand it you draw ...
0
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0answers
26 views

lay stats question

I am comparing two prospective observational cohorts; the "study group" (n=30) has undergone previous intervention that "failed" and has undergone a 2nd intervention. This is being compared with a ...
1
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0answers
32 views

How to pool the interquartile range for an arbitrary distribution?

Let's say that I want to estimate the temperature in an annulus-like region. I split the annulus into four equal sectors (sectors 1,2,3, and 4) with $n_i$ being the number of measurements in sector ...
1
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1answer
45 views

Using nonparametric tests with small samples even when data are normaly distrubuted

Is it appropriate to use a nonparametric test with a small sample (e.g., less than 65 people) even when data are normally distributed? For example, using the Spearman correlation? Actually my data is ...
1
vote
1answer
34 views

nonparametric method to calculate the probability how alike two samples are

I have two samples with each couple of hunderd observations. I want to calculate a probabilty how much they look alike. I'm aware of tests like kolmogorov smirnov but I don't think I need this. I ...
0
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1answer
33 views

Likely mean of a multinomial distribution with dirichlet prior

I am working to create a Bayesian non-parametric estimate of the mean of a distribution given a distribution of observations. Ultimately I'd like to get to a credibility interval of the likely mean of ...
2
votes
1answer
25 views

What does “CRP is a marginalized version of PYP” mean?

I've been reading this phrase and I don't know what it means "CRP is a marginalized version of PYP". What are the parameters/latent-variables we are marginalizing out to drive CRP from PYP?
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0answers
22 views

How to perform Friedman's test with covariates

I have 500 participants who each completed 30 trials. In each trial they need to choose the correct image out of three (a three-alternative forced-choice task). Of these thirty trials, 10 trials ...
3
votes
1answer
54 views

Why are there two forms for the Mann-Whitney U test statistic?

I have encountered two forms for calculating the two-sample Mann-Whitney U test statistic, which are: $$U_1 = R_1 - \frac{n_1(n_1 + 1)}{2}$$ and $$U_1 = n_1n_2 + \frac{n_1(n_1+1)}{2} - R_1$$ where ...
1
vote
1answer
31 views

What is a one-way ANOVA on the ranks of the observations

While reading this link: http://www.statsdirect.com/help/Default.htm#nonparametric_methods/kruskal_wallis.htm, I came across the following: ...
0
votes
1answer
17 views

Reporting results of a Quade test

I have been scouring the internet to find out how to report the results of a Quade test (non-parametric equivalent of ANCOVA). Does someone have an example that explains this in plain terms? I'm not ...
1
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0answers
16 views

Is it okay to use lots of different statistical tests within the same dataset due to not fulfilling parametric assumptions?

I'm trying to reconcile the results of a study, and the fact that we need to do lots of different types of statistical tests to show a few conclusions in a paper. If the data were normally distributed ...
6
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0answers
69 views

Generalized additive models — who does research on them besides Simon Wood?

I use GAMs more and more. When I go to provide references for their various components (smoothing parameter selection, various spline bases, p-values of smooth terms), they are all from one ...
1
vote
0answers
20 views

Non-parametric effect size

Effect size, as estimated by Cohen's $\delta$, is: $d=\frac{\hat x_1 - \hat x_2}{\hat s_{pooled}}$ Since the numerator is an estimate of difference in location, and the denominator is an ...
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0answers
12 views

Risk in density estimation: grasping the definition

When generalizing estimators to an entire function what is the space in which we perform the integral to obtain the expected value (with respect to this function)? For example, when estimating ...
1
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2answers
81 views

Any other non-parametric alternative to Kruskal-Wallis?

It looks like Kruskal-Wallis is the standard nonparametric test for more than two groups. The problem is that it does not tell which groups are different, except that whether there exists significant ...
14
votes
5answers
324 views

A principled method for choosing between t test or non-parametric e.g. Wilcoxon in small samples

Certain hypothesis tests can be approached using Student's t-test, possibly using a Welch correction for unequal variances, or by a non-parametric test such as Wilcoxon paired signed rank test, the ...
2
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1answer
40 views

How to cope with non-normal ANOVA residuals?

My data follow this outline: ...
0
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0answers
30 views

non-parametric tests with significant difference in sample sizes

I have outcomes from a biological expt., where we have measured DNA lengths that has been affected. For condition1, I have 11 observations (length of DNA) and for condition2 I have approx. 116000. I ...
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0answers
8 views

What options do I have to analyze Non-parametric version of two-factor ANOVA with repetition?

Sorry, my previous question was not very clear I deleted it and am trying again. Question: What options do I have for two-factor non-parametric version of ANOVA with repetition? What is the ...
0
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0answers
24 views

How to make non-parametric distribution estimation with known, limited number of points of the CDF?

Is there any method to make non-parametric estimation of a cumulative distribution function (CDF) which actual points (not a sample) can be calculated numerically? I have a numerical method which can ...
0
votes
2answers
42 views

How to apply Mann-Whitney test Control vs Treatment Group

I have a treatment and a control group: both have pre- and post- values (I tested reading speed). I need to know if there are any significant differences between the groups (or if the treatment group ...
0
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0answers
18 views

Minimum sample size in nonparametric data

My population has more or less 80,000 individuals and I would like to take a small sample with a high probability it is really close to the whole population. The problem is that my data is ...
2
votes
1answer
20 views

How to choose a kernel for KDE

There are a lot of kernels available for a univariate KDE. R uses normal by default, but the efficacy discussion seems to support the use of Epanechnikov. What should influence kernel choice for ...
0
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0answers
29 views

Two-way between groups ANOVA for non-normal data

I'm doing a study on visual selective attention (VSA) and how this is influenced by gender and video gaming. So my dependent variable is VSA (continuous) and my two independent variables are gender ...
2
votes
0answers
30 views

Nonparametric tolerance intervals for discrete variables

Suppose you have a bunch of people rate how much they liked a movie on a discrete scale from 1 to 10, and you would like an interval [l, u] such that with (at least) 95% confidence, (at least) 90% of ...
2
votes
2answers
41 views

Parametric test or nonparametric?

I have 2 groups of sample sizes 10 and 11 respectively. Can I apply a parametric or nonparametric test to find a significant difference in means between the groups?
2
votes
2answers
38 views

Multiple models compared over same data

My question boils down to if I really have to use a multiple comparison adjustment or not, and if so, how I can do this to retain as much power as possible. I have multiple models (say 5) that are ...
0
votes
0answers
12 views

Regression analysis is dependent of non-parametric test result?

If I have two variables (i.e. number of pills and skin sensitivity) and I performed a Kruskal-Wallis or ANOVA which gave me no significant differences in any group. Does it make sense to perform a ...
1
vote
1answer
75 views

How to compare count of two groups?

I have a two groups of data - 1/ All data and 2/ Selected_season, which is only some subgroup of all data. I want to find out: a/ if proportion of BM, HB, etc. groups is the same in All data and ...
0
votes
1answer
41 views

Regression discontinuity

I am analyzing some Stata code for a regression discontinuity analysis. The results of this analysis are presented in table 5 of the Online appendix to “The Effects of a Universal Child Benefit...”. ...
2
votes
0answers
43 views

ANOVA on ranks?

Once in a statistics class I've seen the suggestion that one non-parametric approach for ANOVA would be to perform the ANOVA analysis on the ranks of the original data (basically as an alternative to ...
0
votes
0answers
23 views

non parametric index model (Klein Spady) for more than two choices in R

The np package offers an easy way to fit the Klein Spady estimator for index model on dichotomous responses. How to use the np package to extend these methods to the polychotomous (i.e., more than two ...
1
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0answers
41 views

Glm with Poisson in R with no p-value?

I've been doing glm and thought I had it cracked but looking at some sites for interpreting results I realised R had displayed my results oddly. ...
3
votes
2answers
70 views

Book for introductory nonparametric econometrics/statistics

My work implies a lot of econometrics, and I had a good formation about it. Nevertheless, I am regularly faced with some semi or non parametric techniques (for instance I had to use quantile ...
1
vote
2answers
90 views

Log transformation not making data normal

I have a data set with positive skewness when I log tranform it tends to be negatively skewed. Is there any other transformation that I can use or any statistical method works? Thanks!!!
0
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0answers
20 views

Batched bootstrap for non-parametric confidence intervals

I am conducting multiple experiments on moderately large datasets that run over several weeks. I would like to construct confidence intervals for my estimators which are a mixture of means and ratio ...
0
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0answers
16 views

Friedman/Wilcoxon test. How to enter data for multiple repetitions?

Id like to run a non parametric test such as the Friedman test on a dependent variable of my 8 subjects who have done a task under four different conditions. I only found examples of how to input the ...
0
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0answers
68 views

Can I normalize Ordinal Data

I have ordinal data on three IVs ranging from 1 to 5 as below: IV1: Not at all Important - Very Important IV2: Not at all Satisfied - Very Satisfied IV3: Performs much Worse - Performs much better ...
0
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0answers
18 views

How to judge a nonparametric estimator empirically?

Suppose we have an estimator $\hat{f}(Y_1, \cdots, Y_n)(t)$ for the fixed design nonparametric regression model: $$ Y_i = f(\frac{i}{n}) + \epsilon_i, \; f \in L^p[0,1]. $$ The estimator at hand ...
0
votes
0answers
21 views

Appropriate analysis for this experimental design - non-normal data

I've run an experiment with 8 subjects, which had to perform [a series of 4] navigational tasks under 4 different vision conditions each. The experiment was repeated weekly, 16 times with the same ...
3
votes
1answer
164 views

Non-parametric version of paired t-test (Mann–Whitney U test)

I have data from 100 individuals doing a 2AFC under a control and a manipulated setting. I want to compare the means. I initially used a paired t-test. My supervisor noticed the distributions were not ...
0
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0answers
17 views

Can I examine the confounding effect of variables on non-normal data using Pearson?

I have used Kendall's tau to examine whether there is a correlation between a number categorical variables, as I have a small sample. However, I also want to test whether some variables might have an ...
0
votes
0answers
17 views

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 ...
1
vote
0answers
39 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, ...
0
votes
0answers
18 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 ...
1
vote
0answers
31 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 ...
1
vote
1answer
22 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 ...
2
votes
0answers
20 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 ...