Statistical Analysis Stack Exchange
Statistical Analysis Stack Exchange

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1500 questions
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4 answers

The difference of kernels in SVM?

Can someone please tell me the difference between the kernels in SVM: Linear Polynomial Gaussian (RBF) Sigmoid Because as we know that kernel is used to mapped our input space into high dimensionality feature space. And in that feature…
user3378327
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Intuition behind standard deviation

I'm trying to gain a better intuitive understanding of standard deviation. From what I understand it is representative of the average of the differences of a set of observations in a data set from the mean of that data set. However it is NOT…
sonicboom
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3 answers

Can ANOVA be significant when none of the pairwise t-tests is?

Is it possible for one-way (with $N>2$ groups, or "levels") ANOVA to report a significant difference when none of the $N(N-1)/2$ pairwise t-tests does? In this answer @whuber wrote: It is well known that a global ANOVA F test can detect a…
amoeba
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3 answers

How to judge if a supervised machine learning model is overfitting or not?

Can anyone tell me how to judge if a supervised machine learning model is overfitting or not? If I don't have an external validation dataset, I want to know if I can use ROC of 10 fold cross validation to explain overfitting. If I have an external…
user22062
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Visualizing a million, PCA edition

Is it possible to visualize the output of Principal Component Analysis in ways that give more insight than just summary tables? Is it possible to do it when the number of observations is large, say ~1e4? And is it possible to do it in R [other…
gappy
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32
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2 answers

Three versions of discriminant analysis: differences and how to use them

Can anybody explain differences and give specific examples how to use these three analyses? LDA - Linear Discriminant Analysis FDA - Fisher's Discriminant Analysis QDA - Quadratic Discriminant Analysis I searched everywhere, but couldn't find real…
Andrius
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3 answers

Accommodating entrenched views of p-values

Sometimes in reports I include a disclaimer about the p-values and other inferential statistics I've provided. I say that since the sample wasn't random, then such statistics would not strictly apply. My specific wording is usually given in a…
rolando2
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Bound for Arithmetic Harmonic mean inequality for matrices?

NOTE: This question has originally been posted in MSE, but it did not generate any interest. It was first posted there, because the question itself is a pure matrix-algebra question. Nevertheless, since the motive has to do with statistics and…
Alecos Papadopoulos
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32
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What is the hardest statistical concept to grasp?

This is a similar question to the one here, but different enough I think to be worthwhile asking. I thought I'd put as a starter, what I think one of the hardest to grasp is. Mine is the difference between probability and frequency. One is at the…
probabilityislogic
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Likelihood ratio test in R

Suppose I am going to do a univariate logistic regression on several independent variables, like this: mod.a <- glm(x ~ a, data=z, family=binominal("logistic")) mod.b <- glm(x ~ b, data=z, family=binominal("logistic")) I did a model comparison…
lokheart
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Difference between standard and spherical k-means algorithms

I would like to understand, what is the major implementation difference between standard and spherical k-means clustering algorithms. In each step, k-means computes distances between element vectors and cluster centroids, and reassigns document to…
user1315305
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4 answers

Why are lower p-values not more evidence against the null? Arguments from Johansson 2011

Johansson (2011) in "Hail the impossible: p-values, evidence, and likelihood" (here is also link to the journal) states that lower $p$-values are often considered as stronger evidence against the null. Johansson implies that people would consider…
luciano
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3 answers

Visualizing the intersections of many sets

Is there a visualization model that is good for showing the intersection overlap of many sets? I am thinking something like Venn diagrams but that somehow might lend itself better to a larger number of sets such as 10 or more. Wikipedia does show…
Kyle Brandt
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libsvm data format

I'm using the libsvm (http://www.csie.ntu.edu.tw/~cjlin/libsvm/) tool for support vector classification. However, I'm confused about the format of the input data. From the README: The format of training and testing data file is:
Siddhant Saraf
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32
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4 answers

How to perform dimensionality reduction with PCA in R

I have a big dataset and I want to perform a dimensionality reduction. Now everywhere I read that I can use PCA for this. However, I still don't seem to get what to do after calculating/performing the PCA. In R this is easily done with the command…
Floris Devriendt
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