# All Questions

122 views

### Difference between regression methods

I have a set of data where the response is a proportion. For each event in the experiment, a system will correctly tag X of Y ...
10 views

### How to test for mediation with a continuous mediator and DV, but a categorical predictor?

I want to explore whether attitudes mediate the relationship between employment status and intention to apply to graduate school. (See image below). I planned to use the Sobel Test to explore the ...
26 views

### Observations with very high or very low residuals in regression

If a regression model is applied and there exist residuals that is very high or very low (meaning outliers compared to the others), is it good practice to get rid of those observations and then do the ...
27 views

### Forecasting after Box-Cox transformation

I did a regression and found that my residuals pointed out that my data is heteroscedastic. I applied the Box-Cox transformation and my new model looks as follows, ...
29 views

### Computational Complexity of Prediction using SVM and NN?

I've seen answers discussing the complexity of training SVMs and neural nets, but how about for predicting new responses once a model has been trained? For context, I'm working on an app that should ...
17 views

### Percent error for linear regression model

Suppose I fit a linear regression $y = \beta x + \rm error$. In this situation, $x > 0$, $\alpha > 0$, and therefore $y > 0$. Moreover, the $\rm error$ is normally distributed with mean $0$ ...
13 views

### Times series and starting point incidence

I'd like to modelize the height of a plant which depends on Its aging (in months). The month it has been planted. For instance a plant of 3 months is higher if it has been planted in march than ...
12 views

### Best method of statistical analysis for large dataset of different points

I have generated a set of ground displacements at certain points using two different methods. I am now trying to find a good method of statistical analysis to compare how similar the results of the ...
6 views

### Markov-switching and jump processes

Is someone able to explain the differences between the two to me? Do jump processes not control the parameters and instead describe the measured variable?
8 views

### How to insert output into command line / function [migrated]

I have output ("1b" "2b" "3b" ... "40b") The values are then inserted into a function for further calculations. I am prepping the values with the following code. ...
21 views

### Clustering using density fields

I like to tinker in my spare time with clustering algorithms. Over the past few days I was attempting to tinker with a clustering algorithm using density fields of the data. I tried several ...
15 views

### Using Resampling to understand a large table

I have a data set that is very large. The attributes (columns) are several thousand. Some are sparse others are not. Some are ordinal, others interval, nominal or ratio. The row size is 10s of ...
14 views

### Model matrix of a mixed model

Suppose I have a mixed model like this: ...
23 views

### Plot and interpret ordinal logistic regression

I have a ordinal dependendent variable, easiness, that ranges from 1 (not easy) to 5 (very easy). Increases in the values of the independent factors are associated with an increased easiness rating. ...
9 views

### Nonlinear GMM for Dynamic Panel Data

A friend of mine needs to estimate a non-linear GMM on Panel data. As I have checked, the softwares for Panel GMM only estimate linear forms (STATA gmm, xtabond, ...; R pgmm from plm package). How can ...
7 views

### Is it necessary to sample a raster for spatial regression?

I'm looking to model land cover change using a variety of environmental predictors (e.g. elevation, rainfall, etc.) stored as raster layers. In most similar studies I've found in the literature the ...
8 views

### Difference between fuzzy graphical network , Markov model and Bayesian network

Referring to this answer Difference between Bayesian network and neural network and causal inference, I have come across other graphical models (1) Fuzzy Cognitive Map and (2) Neuro-Fuzzy (3) Fuzzy ...
12 views

### theoretical profile correlation

My data (n > 4000) contains the results of two separate tests (instruments). I have a profile made from likert scales for one of the instruments (S1, S2, ... S20). I want to find the corresponding ...
20 views

### Similarity measure between numbers

I have a huge matrix (10*10k). I'd like to know if there is a way to find similarities between lines. Let's give an example of matrix: 4*5 ...
16 views

I am confused and struggling to read this simple crosstabs. I am trying to create a profile of downloaders. One of the demographics I am looking at is age. Should I be looking at the percentage ...
31 views

### Calculation of standard variance $s^2$

First picture is the question and its answer key: The second picture is my solution: I know that $S^2=\frac{\sum(x_i-\bar x)^2}{n-1}$ But in the answer key, $s^2$ cannot be found in that way. ...
25 views

### Is segmented (piecewise) regression possible with a dichotomous dependent variable?

I have created a model of American cities with a dichotomous Y variable using logistic regression. I have theoretical reasons to believe that the model will differ significantly between larger and ...
32 views

### p-value for weighted Pearson correlation coefficient

I'm computing a weighted correlation coefficient, using the method described here. I'd like to compute a p-value for the resulting r coefficient. How can I do this correctly, given that my r was ...
16 views

### How to obtain the complete model matrix of a mixed model?

Suppose I have a mixed model like this: ...
6 views

### Rearranging 2 discriminant function to solve for 1 parameter (to derive a decision boundary)

I have a task where I want to classify patterns from 2 classes where the samples are drawn from a bivariate Gaussian distribution. I use the 2 discriminant functions ($g_1$ and $g_2$) to classify the ...
29 views

### Measuring Statistical Significance of Binary Classification using Matthews Correlation Coefficient

Based on the following relationship between Matthew's Correlation Coefficient (MCC) and Chi Square: (MCC is the Pearson product-moment Correlation Coefficient) Is it possible to conclude that: By ...
27 views

### Hypergeometric Distribution Question

I am currently doing a self-study question that gave me the following scenario: There are 10 marbles in a jar. 7 marbles are red while 3 are blue. John wants to pick 4 marbles out to give his friend. ...
15 views

### test for variance by using chi square test in R

how can i know if these data -> 93, 91, 93, 150, 80, 104, 128, 83, 88, 95, 94, 97 58, 139, 91 provide evidence that the pop variance is greater than 0.05 (a=0.05) by chi square test in R? please ...
103 views

### Why is optimizing a mixture of Gaussian directly computationally hard?

Consider the log likelihood of a mixture of guassians: $$l(S_n; \theta) = \sum^n_{t=1}logP(x^{(t)}|\theta) = \sum^n_{t=1}log\sum^k_{i=1}p_iP(x^{(t)}|\mu^{(i)}, \sigma^2_i)$$ I was wondering why it ...
12 views

### About penalty setting in package changepoint

I have read the documentation for this package,but there is one place I don't understand, in page 7 the author set the penalty value to 1.5*log(n), where does this "log(n)" originate from? A bracket ...
17 views

### data representation with nominal, ordinal and continuous variables

Suppose I have data of this format: customer, country, location, unit price (discrete set), traffic, etc. (more nominal/ordinal variables) I want to know how country affects unit price, how do I go ...
97 views

### Exponential Distribution PDF: Why multiply by lambda?

Hoping you can help me understand the probability density function for the exponential distribution. Given that the distribution's PDF is described as follows when x > 0: $$\lambda e^{-\lambda x}$$ ...
9 views

### How do i read only lines that fulfil a condition from a csv into R? [migrated]

I am trying to read a large csv file into R. Even though the file is large, I only want to work with some of the rows that fulfil a particular condition (e.g. Variable2 >= 3). This is a much smaller ...
18 views

### Understanding stationarity with Inflation

Good afternoon, Apologies if this question is basic, I have done a lot of research, but haven't found a definitive answer online and so I'm hoping someone might be able to help me here. I am looking ...
21 views

### How do we use logistic regression (scikit-learn) to predict values

Logistic regression can help to predict a value whether it would happen or no. I'd like to know how can I do that using sklearn. I'd like to know the probability if this event would happen or no. I ...
28 views

### Trouble fitting a simple linear regression

I have been trying to do a simple linear regression of x3=Weeks Claimed against x4=Weeks compensated. I am having problems because my residual standard error is very high and also my residuals are ...
6 views

82 views

### Plot Pareto tails in QQ-plot for log-normal distributions

I'm working on samples that I'm trying to fit into log-normal distributions. In some cases, Kolmogorov-Smirnov test statistics is something like D = 0.0056 with an associated p-value of 0. Hence, my ...
15 views

### Why naive bayes classifier cannot perform correctly on 1 conditional probability?

I use e1071 package for naive bayes classification. My dataset is having 2 condition/feature (FF1 and FF2) to predict a class of signal (ELO or FP). When I used the following line of code: ...
39 views

### Factor analysis with binary variables using Stata 13

I am trying to do confirmatory factor analysis on data that is coded binary (0 no, 1 yes). UCLA suggests using a tetrachoric ...
19 views

### Feature selection for one class SVM

I have around 300 features, i need to choose features for one class svm. can some one tell me the ideal algorithm for this use case. I know about that for feature selection regularised random ...
18 views

### Objective function of an SVM [on hold]

I have used the svm function in the e1071 package of R software to model my data using variables selected by my feature selection method. I have obtained predictions from this model using the ...
15 views

### How to interpret results if a reference category of a categorical variable in multivariable logistic regression is not significant?

I am trying to do a multivariable logistic regression and using a normal binomial logistic regression, using binomial variable X (coded ...