# All Questions

136,550 questions
16 views

### Gradient descent with no analytical function f(x)

I find myself in the position of wanting to minimize a numerical function f(a,b) with respect to a and b for which I do not have a the analytical form f(a,b). All I have is f(a,b) for many values of a ...
10 views

### How does H2o handles missing values in DRF?

Just wanted to confirm that the h2o's implementation of RF (DRF) handles the missing values for both categorical and numerical features the same i.e., as a separate category?
6 views

### How to account for experimental errors when computing the derivative of a Gaussian process?

When applying Gaussian process regression upon training data, the covariance function can be generally given in the form: $\Sigma_{i,j} = k(x_i, x_j) + \sigma(x_i) \delta_{i,j}$, where $k$ is a ...
5 views

### How to plot trellis plot in R to compare methods? [on hold]

everyone I want help on how to plot trellis plots in R to compare methods, or anyone who can share any book about trellis plot to compare methods in meta-analysis. Thank you in advance.
7 views

### Comparing meta-analyses with partially overlapping controls

I would like to compare to meta-analyses that have semi-overlapping controls. In this situation, a single meta-analysis cannot be performed. There are known methods for comparing metas of ...
19 views

### I need to use a Wilcox Sign Rank test with unequal sample sizes

I'm analyzing a before and after treatment of farm fields based on runoff from rainfall events. Over 6 different farm fields there were 136 water samples from before the treatment was installed and ...
45 views

### How far apart can the mean and median be in terms of moments of the distribution?

Let $F : \mathbb{R} \to [0,1]$ be the cdf of a (continuous, fully-supported) distribution. Consider the median $m=F^{-1}(0.5)$ and the mean $\mu=\int_{-\infty}^\infty F'(x) x \mathrm{d}x$ of the ...
8 views

### What is Ergodic Variance

I am curious as to the definition of ergodic variance in relation to an estimate of some parameter. It was mentioned to me by a teacher although I have not been able to find any references to it.
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### Dummy variable reference category

As part of my thesis, I am exploring the effect of firm owner type on research and development, which is a ratio. I have a dummy variable of company owner type with 10 categories e.g. Bank, ...
8 views

### What is the difference between interval regression and ordered Probit model? [on hold]

What is the difference between interval regression and ordered Probit model?
32 views

### Comparing distribution with small sample [on hold]

I have to determine the minimal number of random point following a N(0,1) needed to match the true PDF of a gaussian N(0,1) I simulated 1000 times one single point following a N(0,1) in R. Each time ...
10 views

### SMOTE sampling for multi-class data

I have a classification problem with 4 distinct classes, but imbalanced data. ...
31 views

### LSTM Bounded Forecast Time Series

Can anyone please provide a logical explanation as to why an LSTM produces a 'bounded' forecast when predicting over unseen time series data? This behaviour does not seem to occur when using a MLP. ...
10 views

### Regression Discontinuity with binary / categorial outcomes and covariates

I want to conduct a regression discontinuity analysis on various outcomes and covariates. Some of the outcomes and almost all of the covariates of interest are binary. Furthermore 3 of my dependent ...
24 views

### Coefficient of determination in time series models

Nagelkerke's (1991) generalized $R^{2}$ (below) is a modification of the Cox Snell (1989) generalized $R^{2}$ (the numerator in the below) which is a coefficient of determination based on the log-...
7 views

### Handling data where the sample axis contains an elution profile

I have a 3-way data cube, where each sample is a 2D matrix. The sample axis contains samples every n-seconds (n = 7 seconds) but there is an ELUTION PROFILE, where the each sample appears and ...
20 views

### Can an exponential growth curve be called a “stable” trend in business stats?

The context is data science for business, so a good example is user registrations for an app over time. If the growth trend looks like the mock-up below (image description has the numbers I used) ...
25 views

### Combining Classifiers with different Precision and Recall values

Suppose I have two binary classifiers, A and B. Both are trained on the same set of data, and produce predictions on a different (but same for both classifiers) set of data. The precision for A is ...
32 views

### Machine Learning, Imputing values that should be blank

Sometimes data sets contain variables that indicate the presence of an event and the value that represented the event. As an example say a teacher wants to predict the grades of his students. Some of ...
12 views

### recursive function simplified to (geometric or arithmetric) series [on hold]

I am trying to implement a recursive function, but that is too computationally intensive. I think there are certain ways to simplify recursive functions into geometric (or arithmetic) series. My ...
11 views

### Is there a theoretical basis for using partial least squares with categorical responses

I am using what is called PLS-DA in JMP to find a model for predicting a categorical (Positive/Negative) response. The documentation says that the responses are simply coded as 0/1, thereby ...
17 views

### Do reaction times differ for different response types?

I have two different conditions (A and B) tested within-subject with a single binary choice trial per condition. In each of the two conditions, the binary choice is between old and new. My hypothesis ...
35 views

### How can statistics be used to avoid “Lending False Credibility To Decisions We've Already Made”

In light of this article Data Science Has Become About Lending False Credibility To Decisions We've Already Made published in Forbes, I would appreciate input from the statistical and data science ...
12 views

### Applying the Pocock boundary rule when p-value is not set to 0.05

I would like to set my new p-value threshold correcting for both multiple comparisons and interim analyses. In a very easy example with two analyses (1 interim and 1 final) according to the Pocock ...
6 views

### Why do topics found by latent dirichlet allocation correlate negatively?

I am dealing with 14000 documents that I am trying to analyze with an LDA. Also I am trying to interpret the outcome. I notice negative correlations between the topic probabilities. I think I expected ...
3 views

### Measure stability of radiomic features using ICC

I have a question regarding ICC. I want to measure how different MRI T1 pulse sequences affect radiomic features extraction. I have at the moment 7 patients, all of them have T1 SE and T1 GRE scans. ...
25 views

### Does online data augmentation make sense?

Data augmentation is popularly done online as that is how it is typically implemented and suggested in neural network frameworks like Keras and TensorFlow. I have also seen it described in e.g. the ...
14 views

### Using transformation including a permutation matrix to fit a linear mixed model

reference: http://www.stat.wisc.edu/~bates/UseR2008/WorkshopD.pdf from page 97. I want to fit a linear mixed model. $Y|B=b\sim N(X\beta+Zb,\sigma^2 I)$ and $B\sim N(0,\Sigma(\theta))$. Here I choose ...
19 views

### Why is the best prediction for a gaussian process a linear prediction?

I want to understand why, for Gaussian processes, the best prediction is linear. I do not understand its proof. I asked this on MSE but did not get an answer. I do not understand the last 4 lines. ...
22 views

### Combining “unbalanced” likelihoods in a “process-based” model

I have a "process-based" water quality model, which is essentially a black-box full of differential equations describing various chemical and hydrological processes. The model is deterministic and ...
17 views

### Analyse my ACF and PACF

I am new to time series analysis, I tried first to decompose my data using the decompose function in R, hoping I'd get a stationary data in the random obtained. I'm planning to fit an ARIMA model to ...
20 views

### Exclude areas of feature space without getting false negatives

I am using a decision tree classifier to split the feature space according to two classes ( A and B). Events of class A are important and I want to classify all of them correct, i.e. no false ...
10 views

32 views

### On feature scaling and weighting for clustering

The issue of feature scaling and weighting for cluster formation has been widely discussed in several books and papers as well as several questions (e.g. here ). To my understanting, variable range is ...
12 views

### How to deal with a potentially multiple categorical variable

I'm building a model that has, as inputs, some categorical variables. I had already dealt with this sort of data before, and applied different techniques as creation of dummy variables and factor ...
42 views

### Can someone Help me with my Statistics Homework? [on hold]

Teacher was trying to see whether a new teaching mehtod would affect the English scores of students. She knew students taught by old methods had (population mean of 580). She tested her method in a ...
4 views

### Ideas for adversarial attack on input data for more robust neural network classifier

I am generating 10000 matrices of size 12x11 whereby each row corresponds to some summary statistics. I have a multi-lable classification problem. When I train and test my convolution neural network ...
14 views

### its about regression coefficent [on hold]

if b y on x =-5, then explain it??? This "b" is Reg. And "y on x" means reg. line y on x ! { The content in these parentheses is Useless, its just the need of Computer to fill the blank space. ........
11 views

### Within Correlation with ANCOVA or Multiple Regression

i have recently tried to understand a measure for within correlation from the paper (Bland & Altmann, 1995): https://www.bmj.com/content/310/6977/446.full The trouble is, the paper describes ...
21 views

### Residual Analysis assumptions for non-linear regression

I understand Regression analysis relies on the following assumptions about the residuals: Normally Distributed (normal plot of residuals) Be independent of each other (random and data must be time ...
18 views

### Need help with Statistics Wordproblem on effect size and NHST(One sample designs) [on hold]

The average height of males in the population is 68 inches with sd=2.4inches. in a sample of 75 men from Peru the average height is 64inches. Is the height of men from peru significantly different ...
38 views

### Fitting pmf of a scaled Poisson distribution and Python histogram plotting

I have a nuclei meanlife of $550\mu s$, for which I've taken the frequency(rate) to be $1/meanlife = 1818$. I then sampled randomly from a poisson distribution with that frequency, taking the ...
12 views

### How to determine the Optimal Value (Threshold) [duplicate]

I have the following data-set, which consists of Ammonia Value and People Count in a hourly manner (Time-Series Data); ...
65 views

### Negative correlation but positive beta value

I got a negative correlation (Pearson correlation) between two variables but a positive beta coefficient of one variable predicting the other in multiple hierarchical linear regression. Is it ...
8 views

### Interpretation of Feature Importance Statistic

I would like to discuss the managerial implications of the outcomes of a support vector machine model. I assessed the feature importance statistic for the support vector model (package ‘rminer’) and ...
11 views

### Denoising and pre-images in Kernel PCA

In "Pattern Recognition and Machine Learning" by Bishop, the following problem about Kernel PCA is laid out : In linear PCA, we can approximate data points by projecting them onto the $L < D$-...
71 views

### Check statistical significance of one observation [duplicate]

I have got a dataset and I need to check if one specific observation within the dataset is significantly different from the dataset's mean. ...