# All Questions

2answers
78 views

### Propensity Score Matching with time-varying treatment

The basic propensity score matching procedure works with cross-section data (ie collected at a certain point in time). The popular psmatch2 command uses a dummy variable indicating that an ...
0answers
15 views

### Reduction of sparse features for machine learning

I'm trying to use a 1D histogram as a feature for machine learning. A histogram instance can be very sparse and the range of its bins is theoretically unbounded. Moreover it is expected that non-zero ...
0answers
8 views

### methodology for assessing experimental design

I have pre post data for 5 different groups of kids living in different settings (rural, low income, high income, etc). The variables include age, gender, type of setting, treatment (exposure to one ...
0answers
13 views

### Multivariate stats

I have the following data to analyse and not sure what the best method would be. I have percent coverage data for several invasive plant species. as well as several variables including different land ...
0answers
29 views

### SPSS Backward Regression, wrong results?

I'm using SPSS to do very simple multiple linear regression models. Playing with these models I noticed I get different results if I either use the Enter method or the Backward selection. Let's say I ...
0answers
3 views

### Noise Contrastive Estimation gradients

I'm trying to derive gradients of the Noise Contrastive Estimation cost which is referenced at equation 9 in Mnih et. al from equation 8. Can you give me some hint? What I derive seems to be totally ...
0answers
26 views

### How to conveniently add a large set of regressors in R? [migrated]

I have to add approximately 30 dummy variables to a regression. If my variables would be named dummy1 - dummy30, I would denote ...
0answers
58 views

### Has anyone tried to parallelize multiple imputation in 'mice' package?

I'm aware of the fact that Amelia R package provides some support for parallel multiple imputation (MI). However, preliminary ...
1answer
24 views

### different HRs and corresponding CIs with cph and coxph

I tried a model using cph and coxph: ...
0answers
5 views

### Product Lifecyle Prediction using Survival Model

The project objective which I have is to come up with a model which would help forecast products which are close to the end of their lifecyle and need to be replaced. I was thinking whether this could ...
1answer
30 views

### Computing conditional variance

Is there a package in R that does that? How could I compute the conditional variance $\mathrm{var}(y|x)$ of a sample? I also don't know what to do in case where there are not enough $y$ for each ...
1answer
99 views

### Simulation in time series analysis

I want to forecast tourist arrivals using time series analysis I expected to use data from 2000-2013. But due to the civil war, the behavior of tourist arrivals is rather different after 2008. ...
0answers
34 views

### Standard error of slope estimator

Can someone please help explain this. I know the answer is a). Or provide a link with more information. The slope estimator, β1, has a smaller standard error, other things equal, if a) there is ...
0answers
9 views

### NARX model to predict future values

I have this problem , where I have to predict a value of a indicator which depends on 270 other predictor variables. I read the time series modelling and prediction on MATLAB , which took the example ...
1answer
20 views

### Conditional Expectation Constant

If the conditional expectation E(Z|X) is a constant k, what can be inferred about Z? Since this means that whatever the value of x is given, Z is always k, does this imply that E(Z) is equal to k?
0answers
10 views

### Outlier detection in weighted time series

Given a set of observations $X _n = \{x_1, \dots, x_n\}$, and a new observation $x_{n+1}$, we aim to find whether $x_{n+1}$ is outlier. One approach to solve this problem is to check whether ...
1answer
47 views

### Is R software being used for commercial purpose as it is open source

I would like to learn R programming as I am interested in learning new programming language. Is R software being used for commercial purpose especially in financial industry.
1answer
13 views

### Explaining Non-Significant Moderations

Schools often teach us how to conduct and interpret Moderations. What they don't teach us is how to explain why a moderation didn't work out for statistical/methodological reasons. Assuming that the ...
1answer
68 views

### How can I determine if a poker application is “fairly” dealing hands? (Texas Hold Em)

I'm trying to take on a personal project with my new found knowledge (and beginner) in statistics and data analysis. I play an online poker app that is Texas Hold Em' (name withheld) and I suspect ...
0answers
19 views

### In R, when plotting using ggvis, how to specify plot range? [on hold]

When plotting using ggvis(x = ~c1, y = ~c2) the range of both axes are automatically determined. But I would like to show a larger range. How to set it? I read ...
0answers
5 views

### R- yaimpute - standarize value before KNN for imputation

I need to impute data before running a logistic regression. I'm trying the package yaimpute but I realized that it doesn't standarize before imputing. I created a sample matrix to view so: ...
0answers
6 views

### Detecting false positives of a classification algorithm

I run a web service with a lot of users. Some of these users are involved in undesirable behavior (e.g. trolling). I've come up with a classification algorithm to detect these users (and deactivate ...
0answers
4 views

### Printing nested lists using nested functions [migrated]

n = [1, [2, [3, [4, 5]]], [6, [7, [8, [9]], 10]]] In python, I want to write a nested function within the function 'print_list' that calls itself recursively for each sub-list. The nested function ...
1answer
41 views

### How am I using KS test incorrectly in R?

Here are the codes I input into R: ...
0answers
6 views

### SLR Residual Plots vs predictor or fitted values?

In our regression class, the professor said we can either plot the residuals vs the predictor values or vs the fitted values. I asked if there was a difference in the two plots (i.e. might you be able ...
0answers
7 views

### Rcmdr package not installed [migrated]

When I tried to installed Rcmdr package with this command: install.packages("Rcmdr",dependencies=TRUE) I got following error message: ...
2answers
19 views

### Finite Population Variance for a Changing Population

How does the addition of one unit affect the population variance of a finite population if everything else remains unchanged? What are the conditions such that the new unit leaves the variance ...
0answers
12 views

### Sample size for a moderated hierarchical multiple regression analysis?

I am having a challenging time finding out the necessary sample size for a moderated hierarchical multiple regression analysis. The first five steps of the regression will include the 17 variables ...
0answers
23 views

### Is it ok to delete items when Cronbach's alpha is low?

I have used a questionnaire in my research that is showing a Cronbach's alpha of .52, even though it has shown good internal consistency in many previous studies. I can see that if I delete 2 of its 9 ...
0answers
52 views

### Extreme learning machine: what's it all about?

I've been thinking about, implementing and using the Extreme Learning Machine (ELM) paradigm for more than a year now, and the longer I do, the more I doubt that it is really a good thing. My opinion, ...
1answer
107 views

### Probability Homework Question

A researcher is conducting a survey of county residents in a Midwestern state. Foolishly, she uses lists of registered voters as a sampling frame and randomly draws phone numbers and addresses from ...
0answers
54 views

### Regression shows positive linear relationship. Then why this negative equation

I am trying to get my regression right. I want to see, if subs increase how much increase in revenue is seen. The dependent variable is Revenue while the independent variable is subscribers. Least ...
0answers
13 views

### My transfer function has non-stationary inputs, but a stationary output. Should I difference both the inputs and outputs during structure estimation?

I have a system of two inputs and one output that I'd like to model using the following Box-Jenkins transfer function ("dynamic regression") structure: y_t=\frac ...
0answers
28 views

### Help in calculating OLS estimators under certain constraints/modifications

I am new to these forums and to econometrics as a whole. I was hoping someone would be able to give me a nudge in the right direction with this problem. I've done extensive research both online and in ...
0answers
21 views

### Reference for the idea that a simpler model can be used when the range of data values is smaller

When we build a statistical-physical model, generally, a simpler model can be justified when the range of data-values is smaller. I can't be the first person to use this idea, but I also can't find ...
1answer
18 views

### post-hoc for non homogeneous data

Which post-hoc test is used for non homogeneous data. I have checked my data set and they are normally distributes. I used Anova with Levene's test and it showed that my data is not homogeneous, and ...
1answer
36 views

### Breaking black and white captcha

I am looking for a way to break this kind of captcha: I know that there are always 4 digits, in black and white. The image basically consists of an easily recognizable 4-digit code, mixed with a ...
0answers
19 views

### Selection of subset of values to hide a certain value [on hold]

Assume that I have a set of 10 integers: x1, x2, ..., x10. I need to select one of them (e.g. x2) to perform a some computation. To hide that I selected x2, I need to select other values as well. My ...
0answers
22 views

### Meta-analysis: Talking about power and inference (to power)

I need a little help or reassurance concerning how to explain power "to power", i.e. to decision makers that are not well versed in statistics. The problem is this: I have done three empirical ...
1answer
64 views

### Implementation of hierarchical bayesian model produces errors with PyMC

I'm trying to solve an exercise from this book in which I'm supposed to fit data on temperature and elevation in Colorado to this model: \boldsymbol{Y} = \boldsymbol{\mu} + ...
0answers
5 views

### Compressed sensing with prior information on locations of non-zeros

I would like to solve a system of equations $Ax=b$, where I am enforcing that $x$ should be $K$-sparse. However, I also want to impose the additional constraint that for $K_1+K_2=K$ and \$x = \left[ ...
2answers
51 views

### How to check if a series has been seasonally adjusted correctly?

I am a bit puzzled here and would like to understand how to check if a time series has been seasonally adjusted correctly using X-13 Arima. After seasonally adjusting time series using X13-ARIMA ...
1answer
22 views

### Very different Neural Network test errors for same architecture

So I'm doing a time series prediction, and assessing the capability of the ANN to predict that time series. I am using Matlab's neural network toolbox functions, and the training parameters are the ...
2answers
363 views

### For plotting with R, should I learn ggplot2 or ggvis?

For plotting with R, should I learn ggplot2 or ggvis? I don't necessarily want to learn both if one of them is superior in any regard. Why R community keeps creating new packages with overlapping ...
1answer
68 views

### What methods are used in order to prove the independence of two variables in statistics?

I have four variables (attributes) describing student. They are categorical data. I need to prove that these variables are independent. The easiest way (even not sufficient) is to see the ...
2answers
33 views

### Significance difference between the slopes of three regression lines

I have three simple regression models with three different Y (dependant variable) and one X (independent variable). All the slopes are significant. Is there anything called testing the difference ...
1answer
64 views

### How can there be a linear correlation between two PCA components?

I perform principal component analysis (PCA) on a dataset, and then plot the first and the second principal components. I get the following phenomenon: one principal component appears to be a linear ...
0answers
3 views

### analysis strategy for selecting and/or transforming correlated continuous biomarkers to predict binary endpoint

I am given a simulation task to come up with several analysis strategies and compare their relative performances. The horizon is wide open; I appreciate all recommendations of methods and references. ...
1answer
14 views

### Rstan model for a simple mixture of normals

This blog post from Rbloggers describes how to code a simple three-part normal mixture model with known mixing coefficients, means and standard deviations. While it describes the procedures in some ...
1answer
68 views

### are qqplots appropriate for time series?

I've seen that qqplots are a very useful tool to check model assumptions. In particular to analyze the residuals. However, it seems that is based on data ordering and therefore assumes a atationary ...

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