# All Questions

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### SAS Residual White Noise Test and validity of R^2 value

I have fit an auto-regressive model to a data series. The model seems to explain the given data relatively well given that the total R^2 is 0.95. However, SAS has a diagnostic plot called white noise ...
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### Pixel level classification using deep network

I am new to deep learning and have already got my hands dirty with running deep network on MNIST and CIFAR datasets. Is there a way to directly use deep learning for semantic segmentation of image. ...
5 views

### Why does APA suggest to report the F statistic with an ANOVA result?

I probably view it too pragmatic but to me, the F statistic is merely a result of a calculation that is used to (magically) determine the value that I'm really interested in: the p. APA, though, wants ...
7 views

### Unequal Variances: Satterthwaite vs Welch

I'm currently working on a stats analysis that has a small study population, n=50. I've segmented the population into two groups and want to perform some ttests to compare differences between some of ...
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### MICE: what does returned df mean?

In MICE, the object returned by pool() has a component, df, which is included in the summary of the pooled analysis. In my analysis I have about 55,000 cases, but the returned df is higher for most ...
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### how to use SAS to shift cells (to get rid of empty cells) [on hold]

Hi I have some questions about data cleaning. A B C E F 1 2 1 2 4 3 1 6 2 But I don't want the empty cells and would like to shift the cells from left ...
16 views

### How to solve: A * x + y = B, when A and B are known [on hold]

What is the approach you would use to solve A * x + y = B when you have a list of A values and their associated B values? ...
7 views

### Characterizing clusters by separate feature vector scores

Say I have a medium amount of dependent variables in a study. These are scores from questionnaires that have been standardized so all are on a scale from 0 to 1. I have clusters of my patients - ...
4 views

### Can the error variance for a factor in CFA be > 1?

I am doing a CFA for 5 constructs, and all together having 23 items, and each construct having a minimum of 3 items each. The error variance of two items are 1.21 and 1.08. How can the error variance ...
26 views

### Complete ditz on math needs help

If 663 million people don't have an item in the population of 7.3 billion, then 1 in how many people don't have it? What is the calculation I would use? How could I figure this problem for myself in ...
10 views

### Feature that is numeric if true, or single value if false

In regards to feature engineering for machine learning models. I would like to engineer a feature that encodes the following: value can be true and if so it will measure a numeric (maybe ...
11 views

### Survival Analysis/Frailty Model

I am trying to build a probability model for the following situation: I have a very large dataset, whose rows are users and columns are the features. All the users visit a particular store X (once ...
7 views

### Fitting data with interdependence

I have an issue, of which I'm not sure how can be solved. I'm trying to do so with Mathematica (and their stack exchange recommended I try here), but other solutions are also possible of course. ...
18 views

### sigmoid threshold for neural network

I've trained a NN for a few logical linear logical functions. I've used the sign(positive=1, negative=0) function to threshold the hypothesis. (That makes a Perceptron right?) Now I want to use the ...
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### Calculating the formulas in a 2x2 contingency table? [on hold]

If I was given: The total sample size The overall proportion of the sample with the exposure (risk factor) The overall proportion of the sample with the disease (outcome)The odds ratio (=ad/bc) How ...
12 views

### Recurrence or transience of countable state space markov chain [on hold]

Consider a discrete time Markov Chain with countable state space S={...,-1,0,1,...} and transition probabilities $p_{i,i+1}= p_{i,i-1},i \in$ S. Show that chain is recurrent if p=1/2 and transient if ...
7 views

### Checking for compatible conditional models

I am trying to implement MICE in R, using the package mice. I keep reading in papers that if the full conditionals we specify are compatible (they factor into a joint), then our inference is valid. ...
6 views

### Plotting error vs weights for neural networks

What is the better estimate of how well your NN is doing? Plotting how weights change with the number of iterations or Plotting how the error changes with the number of iterations ?!
39 views

### How many sides does a die have? Bayesian inference in JAGS

Problem I would like to do some inference on a system analogous to die with an unknown number of sides. The die is rolled several times, after which I would like to infer a probability distribution ...
14 views

### Under what circumstances will the log of a variable be normal, given that the variable is not normal [on hold]

Let us say there is a variable that is not normally distributed. Under what circumstances will the natural logarithm of the variable be normally distributed? I have seen many articles and papers ...
15 views

### How much memory do I need to filter through dictionaries in python of 5million? [on hold]

I am creating a program that has a lot of data. I am currently running it and its been 10 minutes and its still running probably about to stop it. Anyways, I am trying to make my computer faster at ...
9 views

### Optimization algorithm for dependent outcome variables

I'm in need of an (optimization) algorithm in R that can deal with dependent outcome variables. Let me give you a little example: Lets define some input variables x1, ... , xn and some categorical ...
26 views

### What are the key steps in solving Machine Learning Problem

I am trying to make a summary to myself, what are the key steps for solving a Machine Learning problem. I tried to read good books, talked with peer, discussed many issues here, checked many web based ...
14 views

### When is the scatter matrix in linear discriminant analysis singular?

In linear discriminant analysis (LDA), when there are fewer data instances than the number of dimensions (i.e., when the data matrix is of order $n \times m$ where $n$ is less than $m$), the ...
3 views

### Multilevel moderated mediation with multiple mediators in MPLUS

I'm trying to assess a 1-1-1-1 multilevel model with a cross-level interaction at path a. The moderator is the group mean of one of the level-1 predictors. I'm confused about how to model this and how ...
6 views

### Rank of Between Class Scatter Matrix in Linear Discriminant Analysis

In the derivation for Fisher's linear discriminant (the 2 class problem in particular), I notice that the between-class scatter matrix $S_B$ is said to have rank of at most 1. What is the significance ...
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### Calculating p-value from beta and se_beta

I have a set of beta and se_beta values that I would like to calculate p-values for. I know this should be possible via a z-test, but I don't understand how it works and how to implement it. Any help ...
10 views

### Axes having different scales on a q q plot

I was trying to learn linear regression in SAS using this example When I came to the part about the q-q plot: ...
12 views

### 3-way ANOVA to 2-way ANOVA

I have an experimental design with 3 factors of 2 levels each, which are temperature (a1 & a2), pH(b1 & b2) and food (c1 & c2), so I first ran a 3-way anova. Since in 2x2x2 experimental ...
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### is it ok to check normality for individual groups seperated by within-subject variables in a mixed model rather than the entire dataset?

Wikipedia mentions that it is crucial to ensure normality for within-subject variables in a mixed model. I am interpreting this as I should check normality for my within-subject variables and not ...
12 views

### R - Same Density but different QQ-Plot?

I have data variable corresponding to quotation amount and I want to find which statistic law this variable follow if there is one. It seems that the ...
6 views

### Variance estimator of quadratic term of Cox PH model

I have a failure time data set. I want to fit Cox PH model with quadratic term like $h(t;x)=h_0(t)*exp(x\beta_0+x^2\beta_1)$ What will be the mathematical formula for variance of quadratic term? ...
6 views

### Determining if coordinates in a distribution are significant/goodness of fit

I have a non-normal set of data that has x and y coordinates (a non normal distribution). I'm trying to determine if I can include a few particular data points in my analysis or if I should exclude ...
3 views

### output of doParallel workers [migrated]

Suppose I have a code that does various calculations in a foreach loop, for simplicity let it be this: ...
11 views

### adjusting ties for kruskal.wallis [on hold]

I would like to perform a Kruskal-Wallis test on my data. I chose this test because my data is not normally distributed. As I have identical values in my data I tried to adjust the ties for ...
7 views

### Gaussian Process: How to use GPML toolbox for multi-dimensional input?

I am using MATLAB 2014_a student version I have 198 x 9 training data x (X1,X2,...,X9) and 198 x 1 target data y For now, I got linear equation among training data and target data ,for example, ...
16 views

### HMM with final or absorbing state

I am reading about HMMs and it's unclear to me if they are required to have a final state. In particular I have seen examples of HMMs that have an absorbing state and other examples with no final ...
14 views

### Subset based on maximum difference for one variable, minimum for others

This seems like it should be an easy problem to solve, but I can't think of anything nor can I find anything to help me. I'm working with multiple data sets where I have a series of sometimes ...
10 views

### Confusion about Cross-Validation for Hierarchical Bayesian Regression Models

I had two questions regarding model selection for a Hierarchical Bayesian (HB) Regression Model and the purpose of Cross-Validation. 1). I understand cross-validation as one way to perform model ...
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### what are the assumptions of ridge regression and how to test them?

Consider the standard model for multiple regression $Y=X\beta+\varepsilon$ where: (1) X is $n\times p$ of rank p (non collinearity of predictors) (2) $\varepsilon \rightsquigarrow N(0, \sigma^2I_n)$ ...
15 views

### What test do I use comparing pre and post intervention data? [on hold]

I am doing a health related project at at hospital where a policy was implemented for patients on certain therapy. Data was collected for the number of patients and days of therapy pre-implementation, ...
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### How can get F-measure, precision and re call and also Cluster labels in R

I am new to R. I want to use hierarchical clustering of R to cluster following distance matrix. ...
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### Different results in estimating 3PL model parameters in IRTPRO and mirt(R)

Can someone explain why I obtain different a, b, and c parameters estimates when I use IRTPRO3 and the package mirt from R? The method both uses are Bock and Aiken (1981) - IRTPRO calls BAEM and R ...
11 views

### fixed vs random regression in panel data

Anyone could explain me the differnce between fixed and random effects concerning panel data regressions? With examples? I have actually used panel data regressions for some of my predictive models ...
15 views

### Is this alternative hypothesis possible?

Could anyone check that the alternative hypothesis is valid? I wanted to prove that the "Mahalanobis distance ($\mathbf{T_i} = \mathbf{(x_i - \bar{x})^T \Sigma^{-1}(x_i - \bar{x})}$)" is a Log ...
12 views

### Difference in significance of variables between bootstrap based and usual glm regression

I'm using bootstrap regression lately to get confidence intervals and assess variability of coefficients for glm regressions. I'd like to know how to interpretate the results when a variable is ...
8 views

### Comparison Category Rating (Pairwise comparision) with SPSS [on hold]

I'am new with SPSS (worked with Excel before) but have to use SPSS for my bachelor thesis and got some problems. I did a Comparison Category Rating with multiple Persons (Playing 2 stimuli and the ...
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### WinBUGS - sample from the posterior of exponential distributed survival times

as introduction to WinBUGS, I want to simulate the posterior of the Gamma-Exp-Model. Because the posterior is known, I can varify the result. But the true posterior is always shifted to the right. I ...