Linked Questions

2
votes
1answer
33k 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?
0
votes
0answers
72 views

Interpretation of the Mann-Whiteny U test [duplicate]

The straightforward null hypothesis for the Mann-Whitney U test is that the two distributions are identical. However, many documents (including Wikipedia) also indicate that it is equivalent for ...
286
votes
13answers
167k views

How to understand degrees of freedom?

From Wikipedia, there are three interpretations of the degrees of freedom of a statistic: In statistics, the number of degrees of freedom is the number of values in the final calculation of a ...
240
votes
10answers
138k views

How would you explain covariance to someone who understands only the mean?

...assuming that I'm able to augment their knowledge about variance in an intuitive fashion ( Understanding "variance" intuitively ) or by saying: It's the average distance of the data ...
22
votes
4answers
48k views

Difference Between ANOVA and Kruskal-Wallis test

I am learning R and have been experimenting with analysis of variance. I have been running both kruskal.test(depVar ~ indepVar, data=df) and ...
22
votes
3answers
19k 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} = \frac{...
20
votes
4answers
8k views

Is there any statistical test that is parametric and non-parametric?

Is there any statistical test that is parametric and non-parametric? This question was asked by an interview panel. Is it valid question?
4
votes
4answers
13k views

Unequal variances t-test or U Mann-Whitney test?

I have two independent samples and I need to compare their values, to say if values in the first group are higher than values in the second group. I performed the Levene's test and the variances are ...
3
votes
2answers
8k views

How many « degrees of freedom » should a Wilcoxon rank-sum test have?

I would like to perform a Mann-Whitney U Test (also called Wilcoxon rank-sum test) on a weighted sample in R. Such a non-parametric test is required, as neither of the two variables used follow normal ...
6
votes
3answers
2k views

Effect size for Wilcoxon signed rank test that incorporates the possible range of the attribute

I'm currently working on my master thesis and I'm analysing attributes obtained from digital elevation models (DEMs). I try to compare two point sets for which I extracted altitude values from two DEM ...
2
votes
1answer
5k views

Wilcoxon Rank Sum (Mann Whitney) test-SAS Results Interpretation

I need a clarification on interpreting Wilcoxon Rank Sum (Mann Whitney) test results using SAS. Here is a sample results look like. I am trying to form a hypothesis and interpret the results. In this ...
2
votes
1answer
1k views

Wilcoxon rank sum test methodology

I'm comparing the performance of two algorihtms $A$ and $B$ based on a metric. For each algorithm, I have $31$ independent samples that represent its performance. This samples are grouped in two ...
1
vote
2answers
601 views

what is the meaning of 'normality' as a difference between parametric and nonparametric method? [duplicate]

I'm so confused of the definition of the terminology, "normality". I mean, normality of what? According to central limit theorem, regardless of the distribution of population,the computed values of ...
4
votes
1answer
276 views

What do you do after testing if two non-normal distributions differ?

This is a follow up question to "How do I test if two non-normal distributions differ? I have 13 distributions, . According to the previous question, I should do the following. Kruskal-Wallis test ...
3
votes
1answer
432 views

Hypothesis testing for non-normal data

I'm measuring the error produced by operators executing planar cuts under different guiding systems. I define a target plane and then measure the euclidean distance from uniformly sampled points in ...

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