# All Questions

18 views

### aov() and lme() give completely different results in analyzing repeated measures

I have data consisting of two measures per subject (variable score, measured at Day 0, and Day1 per each subject). There are two groups, and each subject belongs to one of them (variable Group). I ...
34 views

### Is there a statistically significant difference between two methods, which test should I use & am I violating random assumption?

I collected data for every 2016 Republican primary that has available at least 3 polls, according to the polling data aggregated by RealClearPolitics.com. In a spreadsheet for each row which indicates ...
37 views

### Model selection in binary logistic regression

I have 3 possible "final" models in binary logistic regression (N=176, Number of events = 36). Now I am trying to decide which one to select. It´s clear,"All models are wrong, but some are useful", ...
7 views

### Set minimum Leaf size for ctree [on hold]

Is there a method to set the minimum number of samples (leaf size) using ctree (library party) in R cran?
14 views

### Predicting the status of an individual across time [on hold]

In my case my training data frame is like the following : Id|Month|Status|Others 1|01/16|O|X 2|01/16|O|X 3|01/16|O|X 1|02/16|E|X 2|02/16|O|X 3|02/16|F|X 1|03/16|E|X 2|03/16|O|X 3|03/16|F|X ...
12 views

### Is a factor solution with a Heywood case considered legitimate?

I read in an SAS manual consulted here that "Factor analysts disagree about whether or not a factor solution with a Heywood case can be considered legitimate." I was wondering if someone could develop ...
3 views

### What does quantile parameter represent in estimate_bandwidth during Mean Shift Clustering?

I was doing Mean Shift clustering in a set of data with Python Scikit learn.We need to estimate bandwidth during Mean shift clustering.But what does the parameter quantile in the function ...
7 views

### How to calculate variance inflation factor (VIF) for a GLMER?

I've never worked with GLMER models before and I was wondering if calculating VIF is in any way different than in simpler regressions. In R, for instance, I usually use the ...
16 views

### How to automate linear model in R [on hold]

I have a data wherein for a specific brand weekly promotional information are there along with its sales. Now while running a linear model we generally look at the desired signs of the variable along ...
30 views

### How to determine seasonality of a binary variable?

I have a dependent binary variable Y, and an independent date variable X. I want to find out if there is any seasonality (at the year level). A few notes: The binary variable is in my model ...
14 views

### How can I export PCA output data in SPSS? [on hold]

I have performed a PCA to reduce the number of variables in my dataset. Now I want to have new dataset with reduced dimension to perform further regression analysis with other variables. How can I do ...
17 views

### Determining multiple linear regression scores

How do you determine (or extract if already given as an output) the X and Y scores from a multiple linear regression model i.e. in the new space (e.g. using typical linear regression packages in R)? ...
21 views

### How does trend stationary recovers from shocks in long run?

I was trying to understand difference between drift and trend wherein I came across concepts of unit roots and trend stationary. (I haven't read any books on time series, just going through web). ...
5 views

### How to deal with continuous variables with NULL values in prediction tasks?

I'm currently working on a machine learning project, trying to predict the expected revenue from a specific user. I have a long list of features that display the date when the user first performed a ...
10 views

### How can I import these .dat data-sets into R and/or Stata? [on hold]

There are some datasets (gss1.dat,gss2.dat,etc.) in this link, and I want to import them to the programs I'm using (R and Stata).They are contingency tables, in the form of scattered numbers. Could ...
103 views

### How linear regression can be used - explanation for grandmothers

Educational question. Suppose you have to explain linear regression to your granny. She is well educated, she knows even the idea of the hypothesis testing, but before you start to tell her what ...
27 views

### Regression ceoff. p-value as a 'summary measure' of 'indication of relative importance'

I have a paper in front of me (peer reviewed, etc.), which states "comparison of the P values for [the covariates] gives a good indication of the relative importance of each [covariate] for ...
12 views

### How to add stochastic drift in dynamic linear model?

As I'm not able to comment (yet), my question follows the one raised by @mzuba here I would like to use the DLM R package to model the local linear trend model, which unlike mzuba specified, has a ...
16 views

### optimism-corrected regression coefficients?

I used a regularized (LASSO) cox regression to estimate relapse times of patients and used Frank Harrell's bootstrapping method to obtain an optimism-corrected performance estimate of my model. I am ...
16 views

### Jensen Shannon Distance Bounds

I am calculating and graphing various distances between probability distributions. I am really confused about the bounds of the Jensen-Shannon Distance. I read somewhere that the Jensen-Shannon ...
22 views

### Monte Carlo conditional pdf

I have a question which as been bothering me. It's best explained by way of a dumb example: Suppose one wants to compute the value of pi by sampling within the unit square (i.e. ...
30 views

### Role of Central Limit Theorem in creating confidence intervals and hypothesis testing

How is central limit theorem useful in creating confidence intervals as well as its role in hypothesis testing around the population parameter.
45 views

### who can explain the gradient descent to a not -mathematician [on hold]

I'm trying to get a better understanding of a neural network backpropagation neural network and especially the gradient descent. I'm not a mathematician so I can't read or understand the formula's who ...
22 views

### which one is more Efficient estimator on a given data set? [on hold]

I want to know "effiency of estimator" using R or "Relative efficiency of estimators", Here i have 7 co-variance matrix estimators, i want to know which one performed more efficiently then others... ...
30 views

### Bias of moment estimator of lognormal distribution

I am doing some numerical experiment that consists in sampling a lognormal distribution $X\sim\mathcal{LN}(\mu, \sigma)$, and trying to estimate the moments $\mathbb{E}[X^n]$ by two methods: Looking ...
49 views

### How does the support of a continuous random variable change under transformations?

Let $X_1$, $X_2$ have a joint pdf and support set $S$. Suppose random variables $Y_1$, $Y_2$ are given by $Y_1=u_1(X_1,X_2)$, $Y_2=u_2(X_1,X_2)$ where the functions define one to one transformation ...
4 views

### Comparing between group HR for different age strata

I was asked by a colleague if i knew how to test if between group (cases and controls) HR were higher in one age strata than in another. The design: Matched cohorts of cases (with info on debut age) ...
19 views

### Is HoltWinters() inferior to ets()? [on hold]

here is a simple R program using HoltWinters() function.it gives the following error message even for 100 iterations..(but run smoothly for smaller number of iterations)..But ets() handles the ...
16 views

### Should data be normalized before or after imputation of missing data?

I am working on a metabolomics data set of 81 samples x 407 variables with ~17% missing data. I would like to compare a number of imputation methods to see which is best for my data. Is there a ...
7 views

### Extended Cox regression time dependent variables

I have registry data for treatment with a certain drug for a large number of patients from the years 2005-2012. The main research question is whether the treatment is associated with higher mortality ...
316 views

### How do ABC and MCMC differ in their applications?

To my understanding Approximate Bayesian Computation (ABC) and Markov Chain Monte Carlo (MCMC) have very similar aims. Below I describe my understanding of these methods and how I perceive the ...
7 views

### exporting from R objects of class “gts” “hts” [on hold]

I am trying to save my forecast of class "gts" "hts" from R into excel but I get an error in R - "cannot coerce class "c("gts", "hts")" to a data.frame". Thank you, Despina
18 views

### What is the state-of-the-art non-parametric PDF estimation?

Below is some data points that are generated by a process that is normally distributed with $\mu=5$ and $\sigma=0.5$. But of course, we will pretend that we don't know the true distribution of the ...
21 views

### Numerical integration of a function of an empirical CDF

I have the following equation $y = f(x)$ and I want to invert $f(\cdot)$ to find $x$ numerically. Because the function $f(\cdot)$ is quite complex I will solve $y - f(x) = 0$ instead, using the ...
18 views

### Poisson regression with offset vs logistic regression

I am thinking to use Poisson regression with an offset variable instead of a logistic regression in case where event is rare, since p (probability of success) is very small and n (sample size is ...
3 views

### Can we do use convenience and purposive sampling at the same time?

Easy accessibility as the reason for choosing the participants but at the same time samples that have been purposely selected
12 views

### How to deal with interaction between several dummy variables and one continuous variables in one or two regression models?

I want to know the relationship between revenue and cost in several conditions. Dependent variables is REVENUE.REVENUE is a continuous variable from 0~1000+.I have several key independent variables: ...
10 views

### How to perform multiclass SVM classification using k-fold cross-validation and SMO with some kernel method in MATLAB?

I have data matrix X.csv file of size nxd, where n are the observations, and d variables. There are c_1,..., c_m classes. Let, Y be the matrix containing the class labels. There is no header row in ...
23 views

### Convergence in hidden markov model

I have a HMM where forward-backward probability increases in Iteration 1, then it decreases and then increases (as well as converges). Probability values after iterations 0,1,2,3,4 are: ...
16 views

### Proving that largest root (obtained via P.C.A.) is a symmetric function [on hold]

Suppose, we are given $\textbf{X} = (X_1, X_2, \ldots,X_m)$ and $\textbf{Y} = (Y_1, Y_2, \ldots, Y_n)$. Also, we are given, S = pooled variance. If we implement Principal Component Analysis (P.C.A.) ...
57 views

### What is the alternate hypothesis of the null hypothesis β_1=β_2=β_3=0?

Usually with simple hypotheses I will have something like $$H_0: \beta_1 = 0 | H_A: \beta_1 \ne 0$$ But suppose I have a null hypotheis $$H_0: \beta_1 = \beta_2 = \beta_3 = 0$$ Question What is ...
12 views

### Reduction of models

In a normal linear model, I have working with 3 categorical factors, $A, B, C$, and my main model is the interactions model $A*B*C$. My question is as follows: If i wanted to see how far I can ...
10 views

### Feature selection for an ordered logit model (R)

I'm using an ordered logit model to predict credit ratings/risk (1-8, ordinal) as a function of 126 predictor variables. (See: https://www.kaggle.com/c/prudential-life-insurance-assessment/data for ...
27 views

### Non-parametric density estimation: Is it better to estimate a PDF by first finding its CDF?

By better I mean fewer density error against the true PDF. Say that $X$ is the random variable that we wish to find its true PDF $f_X$ by the estimation $\hat f_X$. Then my goal is to find $\hat f_X$ ...
20 views

### Principal Component Analysis: Scale reliability and validity

I'm using a popular psychometric scale, the Domain Specific Risk Taking (DoSpeRT) scale, that contains 30 items that measure an individual's risk taking capacity across five different dimensions: ...
23 views

### What statistical tests to compare two AUCs from two models on the same dataset?

Let say I build two machine learning classifiers, A and B, on the same dataset. I obtain the ROC curves for both A and B, and the AUCs value. What statistical tests should I use to compare these ...
11 views

### Applying Cox Proportional Hazards Model on Discontinuous Variable

I am using coxph in Rstudio to apply Cox Proportional hazards model on my data. This model is easy to use on continuous variable ...
31 views

### Is this controversial that in PCA, we want the variance as large as possible, while in bayesian, a large variance means a low precision?

I am wondering about the variance. We say the variance is inverse proportional to precision, then we also say the variance is proportional to the information, which means that a large variance means ...