All Questions

140,566 questions
8 views

Tensile test results

I am currently writing my thesis, where I have to investigate if a surface treatment increases the adhesion (between tape and a plastic surface). For this purpose, I have among other tests, performed ...
6 views

Accounting for peer feedback (nested multilevel)

I was trying to figure this our for a week now, but I am still confused. Perhaps someone can help me here. I have self-reported personality indicators per individual (IVs) and then perceived behavior ...
6 views

How to do post-stratification weighting in sampled groups with low or zero cell populations?

Let's say you received data from a sample. You don't have information on the sample design, but you have population data so you want to employ post-stratification weights to better align the sample ...
19 views

Using multiple regression analysis to predict pricing

I am working for a company that bids on projects with a 30% markup. I want to run a multiple regression analysis on bid pricing. I was planning on using the following for my data: Dependent variable: ...
21 views

How do I specify a correlation matrix in univariate linear regression to account for known correlations between data points? [on hold]

I'm interested in testing whether sex differences (in birds) for a bunch of traits are explained by contemporary selection pressures on those traits. That is, for Trait(i), does the correlation ...
24 views

Why are polynomial activation functions not used

Why are polynomial functions bad as activations?
16 views

Finding a small description length/compression of variable length lists of rational numbers [on hold]

Suppose we have data in form of variable length lists of rational numbers where the order in which the numbers are listed is arbitrary. What is the best way to represent/encode this data so that all ...
15 views

Can Latent Class Analysis entropy be infinity? And what does it mean?

I recently ran a latent class analysis with polytomous outcome variables with the poLCA R package. The model ran fine converged from 2 to 6 classes (the model converged with more classes but fit ...
7 views

Parallel analysis for principle components analysis and Multi-dimensional scaling

Does the same method for conducting a parallel analysis for principal component analyses apply to find the cut-off point for multidimensional scaling? Under the pretense that PCA and linear MDS are ...
27 views

Model Selection with Time Series Analysis

I'm new to time series and would like some help to determine the parameters for my analysis. I have minutely data for a few months and this is how a random week looks like. I ran the Augmented ...
5 views

How to interpret the transition and feature weights in a Conditional Random Field model?

Conditional Random Fields model have been a popular method for Named Entity Recognition as it accounts for statistical dependencies between entities and can include observed features that can aid with ...
13 views

When to use Normalized Root-Mean-Squared Error vs Spearman Correlation?

I am doing some Machine Learning experiments with Azure and the graphs that it gives me are measured in Spearman Correlation vs Iteration Number (part of the machine learning) However I was just in ...
16 views

Variational Autoencoder - How many Normal Distributions for Posterior

I am currently reading about variational autoencoders. Some of the papers I've read are Tutorial on Variational Autoencoders by Doersch: https://arxiv.org/abs/1606.05908 Auto-Encoding Variational ...
16 views

Is there any difference in Trend Analysis and Time Series Analysis?

I want to compare prevalence of disease over time (years). I google "trend analysis" and first results where explaining "Time series analysis". Is there any difference in Trend Analysis and Time ...
13 views

Bayesian ZIF negative binomial regression priors

I'm currently searching for some literature on the efficacy of various non-informative priors on zero-inflated negative binomial regression. However, most of the research I can find provides ...
9 views

Tagging negative examples in a multi-class classifier?

I'm trying to train a text classier to tag chunks of text with an ID representing the topic being described in the text. I have a large corpus of tagged examples to train it with, and I'm using scikit'...
56 views

How should I account for repeated measures in a mixed effects model in R?

I'm new to linear mixed-effects models and I was wondering if I could get some help in getting my model to properly work. I have an example dataset: ...
8 views

Why is there no Standardized Coefficient for Beta0 [on hold]

Can someone explain why there is no standardized coefficient for Beta0? Thank you in advance.
22 views

Probabilities in a multiple choice test

70 students take a multiple choice test with 100 questions. Each question has 4 possible answers— a, b, c, d — and there is only one correct answer per question. Student 1 gets 22 wrong answers and ...
16 views

Help on Object Detection using YOLOv3-tiny [on hold]

Please I need help in understanding what is going on. Specifically, why the offset in the bounding boxes is more pronounced for objects that are to the right/bottom of the image/frame. I retrained ...
17 views

Normalization of Non-Normal Data to 0-1 for use in Multi-criteria Evaluation [on hold]

I have four criteria I am using for a multi-criteria suitability analysis. They have varying scales, so I have used min-max feature scaling to normalize each indicator on a scale of 0-1. I then ...
4 views

How to normalize data by mapping data points from one mixture of multivariate normal distributions to another mixture

How to normalize data by mapping data points from one mixture of multivariate normal distributions to another mixture Problem description I am trying to normalize multivariate time series data. The ...
24 views

How to predict on test test by ARIMA in R [on hold]

I have analyzed the stock price for the forecasting stock price. I have split data into train and test set. I run ARIMA on the train set. But how can I forecast on the test set
22 views

Variance of Mean Response at the Mean of the Data

My question concerns the variance of the mean response as outlined in this short article or in this Wikipedia entry. Basically, the variance of the mean response is given by \text{Var} \left(\hat{\...
41 views

Percentages as both dependent and independent variables [on hold]

I need to do different types of regression: dependent variable expressed as percentage (continuous in [0;1]), independent variable is a running variable (continuous in [0;+inf[) both dependent and ...
10 views

Debiased regularised regression (elastic net)

I have ~55,000 binary observations and 12 explanatory variables (EVs). I am looking to perform variable selection, followed by inference on the effect of the retained EVs on the binary outcome. Since ...
5 views

When comparing classificators, is McNemar's test applied to the output or to the hits?

Suppose I have the following output, alongside the ground-truth ($GT$), for two classifiers $C_1$ and $C_2$: ...
6 views

Diagnostics for first and second order (weak) stationarity

I am currently running a time series analysis which is mostly exploratory in nature. The data consist of a single sample of a univariate time series (equally spaced) and contains about 200 data points....
19 views

Simple slopes after rescaling variable

I ran a regression model with a dichotomous predictor (x) and a continuous predictor (z). Following advice here, I rescaled both regression inputs by 2 standard deviations and centered them at the ...
3 views

Error margin calculated from individual errors/residuals

Say I run a model and then calculate the residuals or the errors between what my model predicted and the real-world results. For example: ...
24 views

Classifying feature vectors just using a probabilistic classificator for the iris dataset [on hold]

I would like to classify the iris dataset and subsequent vectors from an estimation or guess of the iris dataset distribution. I would like to compare the performance with a neural network. I would ...
13 views

Permutation test for accuracy in multiclass discrimination

It is well known that to assess the significance (i.e. difference from chance) of the performance of a classification analysis one can use a permutation test. In a two-classes case, the procedure is ...
16 views

Theory : possibility to get probabilities from tree methods with unbalanced data classes?

I am working with C5.0 from the C50 R package. I try to predict a binary output from severly imbalanced data classes (~ 2% of "1"). Without weighting the train variables, or adding a cost on type I /...
7 views

It is possible to calculate what the expected hazards ratio would be for a subgroup if I am assuming the subgroup is an independent variable?

I am interpreting a placebo-controlled comparative study. For the primary endpoint: Overall n=8179 Hazards ratio: 0.75, 95% CI: 0.68 - 0.83 Gender is assumed to be an independent variable in ...
7 views

How to appropriately apply activity probability distribution to location probability distribution?

Given the probability that an individual was in a particular area during an hour of the day and the probability that the sample population was doing an activity at an hour of the day, how would one ...
18 views

Reconciling various definitions of Variance Components

In the context of multilevel modelling, Field (2013) p. 827 provides the following representation of a variance-covariance matrix to illustrate Variance Components and writes This covariance ...
30 views

Interpretation of the trend coefficients in log-linear model

I want to estimate price of a product, lets say a boat, over time - panel data model. I estimated a model where I control for number of characteristics denoted as $X$ ( e.g. engine size, weight etc.)...
2 views

From what aspect to measure the performance of an object detector?

I am on the hook to measure the prediction results of an object detector. I learned from some tutorials that when testing a trained object detector, for each object in the test image, the following ...
75 views

If $X$ and $Y$ are independent variables from each other, then are $(X,Y)$ and $X$ necessarily independent?

If $X$ and $Y$ are independent variables from each other, then are $(X,Y)$ and $X$ (necessarily) independent? Assume one is trying to analyze the effect of peer education (education from patient to ...
7 views

Checking association between each category of a variable and disease outcome

Suppose a disease can have four different outcomes: Normal, disease_status_1, disease_status_2, and disease_status_3. Let I have two categorical variables in the model: sex (male or female) and age (&...
14 views

Problems when forecasting with tslm when I include bizdays and easter as variable? [on hold]

I am having problems when I want to forecast by using tslm. My data are monthly data and have seasonality and trend. Moreover I want to consider the bizdays() function and easter() as variables in ...
43 views

interactions involving two continuous predictors with emtrends

Let's say I have a model with two continuous predictors (nitrogen and temperature) and one categorical variable (variety). <...
10 views

Minimum number of data points for clustering (Kmeans, DBSCAN, Isolation Forest) [duplicate]

I'm trying to do some clustering to find anomalies and the number of data points varies a lot (from 2 to 1000 data points), with two or four features. Is there a lower bound for the number of samples ...
15 views

What is the proper statistical test to apply for this scenario?

I have measured the activity of an enzyme with two different substrates. I did this at 7 time points (t = 0, 1, 2, 3, 5, 15, and 30 minutes). I repeated this experiment 3 times for each substrate and ...
7 views

Intuition for nonmonotonicity of coefficient paths in ridge regression

Intuitively, why may some of the slope coefficients in ridge regression increase in magnitude when the penalty parameter $\lambda$ is increased?
9 views

Correct terminology to refer to a collection of conditional probability distributions

I would like your help to find the correct terminology to refer to a collection of conditional probability distributions. Consider two random variables $Y$ and $X$, with supports $\mathcal{Y}$ and \$\...
9 views

Multiple & multi-step time series forecast training data with RNN

I have read a lot of discussion on how to do cross-validation on time series data (e.g. walk forward) but I failed to understand how to properly prepare the training data for multiple time series ...
28 views

Appropriate action to take once I've run 30 regressions with same IVs but tweaked DV

I run 30 OLS and GLM regressions using the same 9 IV/variables/features, but each with a slightly tweaked DV/target/label. More or less the same same variables are significant each time, but DV-tweaks ...
27 views

Value of normal distribution

Can anyone tell me what will be the exact value of zα at a 95% confidence limit?? zα is the standardized normal variable with (1 − α) confidence level. I am using this equation to find limits for Q-...
22 views

identifying what has changed in the data year on year

I have a dataset from one year and the 'same' dataset for the next year. I would like to identify what has changed in the datasets between the years. Both datasets have the same columns. I currently ...

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