3
votes
3answers
37 views

The sum of two symmetric random variables is symmetric

If $X$ and $Y$ are two random variables with probability density functions which are symmetric around their respective means, their sum, $X+Y$, has a probability density function which is symmetric ...
0
votes
0answers
2 views

What do I do with zero columns in a tensor.prod.model.matrix?

Suppose my two marginal bases are given by (for variable $p$ and $t$ the degree is equal to $1$ and $5$ inner knots are used). ...
0
votes
1answer
1 views

Converting a set of tweets into vectors for clustering

I have a large set of tweets to which i plan to use cosine similarity to cluster the tweets. I found NLTK's GAAC to be good but how do i convert the tweets into vectors? In ...
0
votes
0answers
3 views

Efficient evaluation of multidimensional kernel density estimate

I've seen a reasonable amount of literature about how to choose kernels and bandwidths when computing a kernel density estimate, but I am currently interested in how to improve the time it takes to ...
1
vote
1answer
2 views

How to estimate confidence level for SVM or Random Forest?

I have two classes (say 1 and 0), and want to build a classifier. It is possible to use ...
3
votes
0answers
26 views

What is the relationship between the GINI score and the log-likelihood ratio

I am studying classification and regression trees, and one of the measures for the split location is the GINI score. Now I am used to determining best split location when the log of the likelihood ...
0
votes
0answers
13 views

Using a Decision Tree Algorithm such as C4.5 to understand population Partition

I have multivariate data about a certain population with more than 1000 attributes per exemplar. Some of the variables are basic demographics attributes including: gender, age, race, ethnicity, ...
2
votes
0answers
25 views

Is Big Data the end of Statistics?

Statistics emerged as a discipline whose goal was to allow inferences about inaccessible populations from data obtained from its samples. Does modern access to huge amounts of data depreciate the ...
0
votes
0answers
6 views

How to get the overall effect for linear mixed model in lme4 in r?

I would like to get the significant value and effect size of the independent variable in overall, rather than the normal output from lme4 in R. It is just like the thing people report when running ...
0
votes
1answer
1 views

Mean ranks and standard errors of Kruskal-Wallis test

While it's easy to compute the p-value of Krsukal-Wallis non-parametric test using the kruskal.test() function, I don't know how to compute the mean ranks and ...
1
vote
1answer
117 views

How to get confidence intervals for specific indirect effects in Amos?

Say I have an SEM model with 1 predictor variable (IV), 2 mediators (MV1, MV2) and 1 dependent variable (DV). Amos reports combined indirect effects for an IV on a DV. So the combined indirect effect ...
3
votes
1answer
1k views

Calculate standard errors: interaction between 2 factors, one of which has 3 levels in a regression model

I have the following model: $y \sim b_0 + b_1x_1 + b_2x_2 + b_3x_1x_2$. $x_1$ is a factor with 2 levels (0 and 1), and $x_2$ is a factor with 3 levels. I know that to calculate standard errors for ...
0
votes
2answers
10 views

analysing difference in variability between multiple related time series

I have constant time series (yearly from 1950 to 2010) of the abundance of several species that were captured by different groups. These series are somewhat related because the quantity of all species ...
0
votes
1answer
40 views

binary data with no correlation but with p-values equal to real data

For doing parallel analysis in my real data to determine the number of its dimension, i need to simulate binary data matrix with n(number of case) by k(number of items). the p-values of these ...
0
votes
0answers
7 views

Which type neural networks for time series classification

I would like to use neural networks to classification of time series ( I have some Patterns and I want to adjust input time series to an appropriate class) -ist it possible to do this job with ...
0
votes
1answer
24 views

Hierarchical clustering of correlation matrix

I have a correlation matrix of 8,854 * 8,854 size. These are Pearson correlation coefficient values in the matrix. I want to perform Hierarchical clustering and create good resolution images like I ...
0
votes
1answer
81 views

CI for conditional probabilities

I am searching for some information about confidence intervals for conditional probabilities I thought about treating them as normal probabilities with the formula $$P(Y=i|x=t) \pm z \left(\frac{ ...
0
votes
0answers
4 views

Lagrange-Multiplier test for Serial Correlation

When testing whether $\epsilon_t$ is serially correlated in: $$y_t = \alpha + \beta_1x_{1t} + \ . . . \ + \beta_kx_{kt} + \epsilon_t $$ Can we simply test: $H_0: p = 0$ in the following: $$y_t = ...
0
votes
0answers
20 views

What's wrong with my Kernel algorithm (Kernel SVD)?

I have a user-item matrix $A$ as data input, which is a sparse matrix containing a large number of missing values (as zeros). Each row is a user, and each column is an item. Generally, I am conducting ...
2
votes
1answer
36 views

Does it make sense to impute year of birth?

This is data cleaning and preparation stage question for me. I apologize if the question is basic, but I am a beginner. I have a dataset of a bit less than 4500 records. This is a survey and ...
0
votes
0answers
5 views

Discriminant analyses with NIRS in R

I am working with a NIR matrix consistent of 134 rows (samples) and 1529 columns (wavelengths), from which I want to discriminate between two categories (species). I have successfully used the plsda ...
0
votes
0answers
7 views

What kind of test should I do and how many participants do I need for this?

I am designing new functionality in a web application, and I am testing two variations on the navigation to attempt to determine which approach is more successful for our users. I am running the test ...
2
votes
0answers
11 views

How does Factor analysis explain the covariance and PCA explains the variance?

As I read in Bishop's PRML (here is the clip of that part about FA): According to the highlighted part, factor analysis captures the covariance between variables in the matrix $W$. I wonder HOW? ...
5
votes
4answers
140 views

What do these statements not follow logically from a 95% CI for the mean?

I've been reading Hoekstra et al's 2014 paper on "Robust misinterpretation of confidence intervals", which I downloaded from Wagenmakers's website. On the penultimate page the following image ...
0
votes
0answers
5 views

Linear correlation in ANCOVA - necessary?

I've been told by my stats prof that running an ANCOVA relies on a series of assumptions, including that the the dependent variable and the covariate are linearly related. So, in SPSS the first thing ...
0
votes
0answers
3 views

When is Micro-average Precision = Micro-average Recall

This page describes briefly on micro and macro precision used in computational evaluation: http://rushdishams.blogspot.de/2011/08/micro-and-macro-average-of-precision.html This paper surveys the ...
0
votes
0answers
11 views

Should I be using a GLMM?

I'm looking at the influence of pollen type on whether a flower sets fruit (i.e., yes or no = 1 or 0). Then looking at number of seeds per fruit (1-6 possible). I was told I should use lmer, however ...
0
votes
0answers
16 views

Why is the Fisher exact test not always used in the cases where a chi squared is appropriate?

According to Wikipedia: Although in practice [Fisher's exact test] is employed when sample sizes are small, it is valid for all sample sizes. If Fisher's exact test can provide the exact ...
0
votes
0answers
27 views

Is the distribution of my residuals from a multiple regression normal?

I have a dataset with 17 variables (one numerical, 16 categorical). The numerical variable is the execution time of a process. I'm using one of the categorical variables (100 levels) to predict the ...
2
votes
0answers
8 views

prediction from incomplete observations

Suppose I have a linear model predicting class-membership from a set of predictors. Now, I am going to classify a new observation which has, however, some predictor values missing. How can I deal with ...
0
votes
1answer
150 views

How to discretise continuous attributes while implementing the ID3 algorithm?

I am trying to implement the ID3 algorithm on a data set. However, all attributes are continuous and can have values between 1-10. I found that we have to specify the bin intervals for discretization ...
0
votes
0answers
8 views

Linear model in R - 2 fixed and one random factor

I have performed an experiment on plants and have some trouble analysing the data. For the experiment, we have three replicates (in time), two species and three treatments. In each experiment, we ...
0
votes
0answers
6 views

Replicator Neural Network, Step-wise function causing same prediction

In my project, one of my objectives is to find outliers in aeronautical engine data and chose to use the Replicator Neural Network to do so and read the following report on it ...
0
votes
0answers
6 views

Comparing density plots and scoring the combination

I have a set of density plots that contain the distribution of stock prices. Each graph has 5 density plots as follows that shows the distribution of monthly returns based on their ratings - ...
0
votes
2answers
23 views

AB testing with R [on hold]

I'm new with AB testing and i want to do this with R (free and easy to learn software). Can anyone help with sample code in R for AB testing? Thanks Ariel
0
votes
0answers
5 views

Forced-choice data possible with confirmatory factor analysis?

I have a task where I ask participants to view a series of images. After viewing each image they are given several options with which they must a forced-choice as to which category the image falls ...
3
votes
2answers
38 views

How do I estimate the average size of objects

We have a large number of (physical) legal files, and want to get an estimate of the average number of pages per file. I do not know what distribution of pages to expect, the number of pages will ...
0
votes
0answers
12 views

Probability of Event from a Chi-Square Table

I have the following table: From here I want to answer the following question: P(CHILD CAN RECOG BEG SOUNDS OF WORDS – YES | CHILD RECOGNIZES LETTERS - Most of them). From my understanding of ...
0
votes
0answers
9 views

Is it valid to use Hartigans' dip test to reject uni-modal null hypothesis with large N?

first time questioner, so please be gentle :) I have two distributions of data from a simulation. By eye, one looks like it might be bimodal, one not. I copy them below A: parameter value 1 : by ...
11
votes
2answers
354 views

Is the exact value of a 'p-value' meaningless?

I had a discussion with a statistician back in 2009 where he stated that the exact value of a p-value is irrelevant: the only thing that is important is whether it is significant or not. I.e. one ...
0
votes
0answers
6 views

Significance of the distribution of DNA sequences given a certain nucleotide bias

I have a large sequence of DNA in which every position can have 4 different states, or nucleotides (A,T, G or C). The distribution of the nucleotides in the sequence is non-random and, most ...
2
votes
1answer
27 views

Converting log odds coefficients to probabilities

Suppose we've ran a logistic regression on some data where all predictors are nominal. With dummy coding the coefficients are ratios of log odds to the reference levels. A colleague claims that we can ...
0
votes
1answer
23 views

Validity of an iteration for Goodness of fit to a specific application

I am not a statistics expert and would like to check the validity of a test I hav used on a survey results. Survey Results I asked people (n=264) to characterize a panoramic road they chose in 24 ...
1
vote
1answer
52 views
+50

Optimizing through a Transition matrix, in a non-stepwise manner

I made some sort of a transition matrix of an increase in probability of success, given the allocation of some finite resource (e.g. 4 in this case). At this moment, I consider the allocation in a ...
1
vote
0answers
11 views

How to test for serial correlation with pooled OLS, FE an RE?

I have pooled data for 3 years, and I have come across the problem of serial correlation. Some books mention the problem of serial correlation when pooling the data. My question is: is it possible to ...
0
votes
1answer
25 views

How to compare distributions of two groups where each group has multiple observations from a small group?

I have data on continuous measurements (length of time of a behaviour) from two groups of individuals which differ in their phenotype (phenotype A or B, the variable used to group them). Each group is ...
0
votes
1answer
21 views

Five-number summary and mean

Why was not mean included in the five-number summary, when it was first conceived? What was the motivation of choosing sample minimum & maximum, lower & upper quartile and median?
4
votes
2answers
51 views
+50

Standardizing inputs for CART

I know I do not need to standardize the predictor variables before applying CART but would there be any adverse effects to doing it anyway? I'm comparing CART to a linear regression where I did ...

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