# All Questions

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2 views

### Subject-specific predictor centering based on observed value of dependent variable

In a study on human movement mechanics, my variables are 1) an indicator of performance, and 2) a vector describing one's average body configuration. Hundreds of observations are recorded for each ...
8 views

### Why might stacked generalization not be working?

I have a dataset of around 10,000 rows, with 500 features, response variable is binary classification. I split the features into 5 equally sized groups (based on subject matter expertise), and trained ...
6 views

### Normalizing daily data to simulate, and then de-normalize, N-day data

I am attempting to model an N-day joint density for a portfolio of assets. To keep things simple, I have assumed a Gaussian copula but have gotten pretty unrealistic results assuming lognormal returns....
10 views

### Find the simple regression formula

I need help finding the simple regression equation. Those were my calculations, I am not sure if it's right:
24 views

### Confidence interval / p-value duality: don't they use different distributions?

Idea: p-value is less than the level of significance if and only if the corresponding CI does not include the null value; and vica versa, the p-value is greater than the level of significance if and ...
6 views

### can daily count data use GAM ordered categorical family, proportional-odds model?

The observed response variable Y takes on one of K(=21) ordered categories. Here is a summary of my response data (count data: the number of hospital admission in each day), y has observations across ...
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### R error when running BFAST for breaking points detection [closed]

I am encountering the error below when I try to use BFAST detecting breaking points for my time series. Error in cut.default(cycle(y), if (sbins > 1) sbins else frequency(y) * : invalid number of ...
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### Comparison between regression models based on trees

I'm solving a prediction problem in which I have an independent variables Y and 13 dependent variables which also are highly correlated. My dataset is composed by 124 observation for the train dataset ...
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### What is a good binary_crossentropy or categorical_crossentropy?

I am training a binary classification model using LSTM and the training binary_crossentropy loss went from 0.84 to 0.83. I want to know what is a good binary_crossentropy loss value? There seems to be ...
6 views

### What does it mean that "a fixed effects model ignores the information on repeated measures"?

I am trying to justify why a mixed model with random intercept would be better and I came across this sentence. I think it refers to the fact that the scores on the dependent variable for each ...
7 views

### How to use frequency weights in an mgcv multinomial GAM fit in R

I was wondering if it is possible to use frequency weights in an mgcv multinomial GAM fit (i.e. using weight=the count of that outcome, ...
4 views

### prove first order stochastic dominance [closed]

Let Y be uniformly distributed on [0; 1]. Then, for any e > 0, there exists a random variable X such that (a) X >(first order stochatic dominant )Y ; (b) P(X < Y ) = 1 -e ".
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### Which standard errors?

Guten Tag community from Germany :) I'm working on a project with panel data and decided to use the fixed effect model, because the hausmann test p-value < 0,05. No I wonder ho do I know, which ...
8 views

### Can we recover joint distribution from a continuous range of convolutions?

Given a correct model of the joint distribution of a random vector $(X,Y)$, we can derive (though not necessarily in closed form) the correct distribution model for $pX+(1-p)Y$ for any $p\in[0,1]$. ...
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### Copula for 3 variables

I want to make Copula analysis for 3 variables to understand the dependency. I applied following code to obtain $c_{1,2}$ and $c_{1,3}$ ...
23 views

### When can I say there is no clusters?

I am trying to do a clustering analysis for a very small data set (<100) in higher dimensional feature space. I tried K-means and Hierarchical clustering, but I found no 'elbow' and also the ...
15 views

### Power calculation for non-normal distribution

I'm trying to do a power analysis for a research study aimed at characterizing between group differences in depression for 2 different populations. As I understand it, depression scores are a non-...
8 views

### What is TN rate in Weka results?

I have a question about classifications model in Weka. Which parameters in the result from weka is the TN rate(specificity)?
11 views

### weight-tuning for mean [closed]

Let’s say I measure a variable $V$ between two groups $A$ and $B$, and there are some effects that I want to put into account, for example, if I measure students memory of some topic over two periods ...
4 views

### Incremental impact of adding a categorical variable to a mixed model

I feel somehow like what I want to do here should be something quite standard, but I can only think of slight fudges or long routes to the end goal. We want to try to justify the collection of an ...
17 views

### What are the best ranking models availble?

I am looking to compare data for example with sports teams, compare recent and historical results. I want to be able to compare any two teams when needed and also take into account a players database ...
17 views

### Calculating a 95% confidence interval without the original dataset

I have been asked to calculate a 95% confidence interval based on the following paper: https://www.nber.org/system/files/working_papers/w26107/w26107.pdf The question reads: Suppose rainfall in the ...
9 views

### Usefulness of identifier variables in ML model building

I have a dataset with 1000 rows and I have an identifier variable called person_id. May I check why is it told that we should remove identifier variables from ML ...
5 views

### Likelihood of True Positive only from TPR and FPR

When preparing for an interview, I got the following question (on this medium link), Given a medical test produce a 1% False Positive rate (FPR), and the population True Positive Rate (TPR) is 5%, ...
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### Tobit panel data or panel data with trunced dependent varibel

Does anyone know if it is possible to use the Tobit model and the data panels model together, especially in the R language? I tried the censReg package, but it didn't address the inherent testing of ...
14 views

### variance of a vector in Python numpy

I want to calculate the variance of vector [0, 3, 4] in Python numpy. My code is test=np.array([0, 3, 4]) print('test var', test.var(axis=0)) The output is ...
11 views

### How do we call the distribution of a constant divided by a truncated normal distribution?

I have been thinking for a while about the following problem of Cohen's d effect size measure $d={\frac {\mu _{1}-\mu _{2}}{\sigma}}$ in random-effects meta-analyses for which I cannot find a more ...
12 views

### Log Naive Bayes NLP dropping the denominator [duplicate]

I'm learning about the the Naive Bayes classification and I don't get what the squiggly alpha sign means and what it means that "Denominator remains constant for given input." Is it because ...
7 views

### When A/B testing is not possible

I need some methodological advice : I have a population which at a certain time received a treatment (I use clinical terms for practical reasons). I have then been asked what was the effect of the ...
11 views

### Standardisation and Logistic Regression

I read that "Standardization isn’t required for logistic regression. The main goal of standardizing features is to help convergence of the technique used for optimization." Although Logistic ...
9 views

### I only have binary independent variables in OLS - how can i test for linearity?

I have created an OLS regression model, to predict the change in consumers prices at fast-food restaurants and all of my independent variables are binary (either 1 or 0), for convenience i have ...
7 views

### code for hit in black jack [closed]

I am struggling with Q8, Just put Q7 since Q8 depends on the function in Q7 Question 7 (2) Define a function called hit. The function ...
32 views

### How to interpret feature hashing ouptut?

I am working on a binary classification problem with 1000 rows but have multiple high cardinality variables. So, I decided to use Hash encoder to avoid curse of dimensionality. However, after feeding ...
11 views

### data that is not normally distributed - using nominal and ordinal variables

Im a statistics novice and am trying to wrap my head around normal distribution. If my data is negatively skewed and uses nominal and ordinal data can I use a Chi-square test of independence? How does ...
14 views

### Notation used in time series

I found this wikipedia article about the concept of stationarity in stochastic processes. Let $\left\{X_t\right\}$ be a stochastic process and let $F_{X}(x_{t_1 + \tau}, \ldots, x_{t_n + \tau})$ ...
22 views

### Can one specify a fractional degree of freedom for a constrained parameter?

There is a good explanation of degrees of freedom elsewhere. But which heuristic applies in the following is not so clear from that explanation. There is also a different question elsewhere. Is there ...
12 views

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### No Free Lunch Theorem and Random Search

Recently, I posted a question about a very interesting property of the Random Search Algorithm (The "Amazing Hidden Power" of Random Search?), in particular - in the context of function ...
9 views

### On distributions over orthonormal sets: existing families, construction, and simulation

Have families of distributions over orthonormal sets been defined and studied in the literature? What are a couple examples and/or references? Are there known methods for constructing distributions ...
22 views

### Why do we always illustrate and depict the Loss Functions of Neural Networks as Non-Convex?

Why do we always illustrate and depict the Loss Functions of Neural Networks as Non-Convex? By doing a quick Google Images Search of "Loss Functions for Neural Networks" - we are generally ...
7 views

### Do we know the Effects of "RELU Activation Functions" on the Convexity of the Loss Functions in Neural Networks?

Do we know the Effect of "RELU Activation Functions" on the Convexity of the Loss Functions in Neural Networks? I have heard the following argument being made regarding Neural Networks: ...
9 views

### Are there any Statistical Models that can solve the "Wolf, Goat and Cabbage Riddle"?

Are there any Statistical Models that can solve the "Wolf, Goat and Cabbage Riddle"? I have heard of a famous riddle called the "Wolf, Goat and Cabbage Riddle" (https://en....
39 views

### Why is "Jensen's Inequality" Important in Probability?

Why is Jensen's Inequality Important in Probability and Statistics? I was reading the Wikipedia page on "Convex Functions" (https://en.wikipedia.org/wiki/Convex_function), and came across ...
9 views

### What research design?: One sample t-test [closed]

On what research design do one sample t-test and chi-square goodness of fit usually use?
10 views

### Finding Probability normal approximation to binomial method [closed]

Need help in solving a question, i am unable to solve being new to statistics I have given a sample of 20 data points as under: 100.43 95.51 101.02 96.85 93.15 91.69 99.81 98.9 85.42 93.77 93.39 83.41 ...
12 views

### Correct posterior odds in Kahnemann and Tversky example

I am reading the article "judgement under uncertainty heuristics and biases", and in this article they present an example which should underline that people are biased in their evaluations ...
214 views

### Why don't we see Copula Models as much as Regression Models?

Is there any reason that don't see Copula Models as much as we see Regression Models (e.g. https://en.wikipedia.org/wiki/Vine_copula, https://en.wikipedia.org/wiki/Copula_(probability_theory)) ? I ...