All Questions

0
votes
0answers
13 views

Asking opinion about random forests, chi squared and data permutation

I have a set of data of counts of hares in summer and in winter, which is very unbalanced: winter was too cold, and samplings were taken only in some 20 occasions, while during the pleasant summer the ...
0
votes
1answer
7 views

PRISMA Statement: number of records returned by (one/several) databases?

In keeping with the guidelines of the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) Statement, I am trying to fill in their flowchart (Fig. 1) with the details of the ...
0
votes
0answers
25 views

Properties of Nonparametric Test Statistics $B$ [on hold]

Given Consider the upper tail $H_0: \theta \leq 0 \,\,\, \text{vs} \,\,\, H_a: \theta > 0$ sign test with the test statistic $B = \sum_{i=1}^n{\psi_i}$ where $\psi_i = \mathbb{I}(Z_i > \theta)$...
-1
votes
2answers
45 views

can one calculate a p value in a distribution [on hold]

I have an event which happens so many times, I want to know how significantly is 1300$ in comparison to the distribution. which test should I use ?
0
votes
0answers
5 views

Linear discriminant scores using caret

I'm using the caret package in R to undertake an LDA. I'm having problems trying to extract the linear discriminant scores once I've used predict. The model is ... ...
0
votes
1answer
21 views

Closed-form solution to least squares with a matrix of parameters?

I'm familiar with the closed-form solution of ordinary least squares which minimizes $\sum_{n=1}^N(y_n - \mathbf{\beta x_n})^2$ for scalar $y_n$. However, in my situation I am trying to fit some data ...
0
votes
1answer
14 views

Statistical significance in sales - test vs control

I have a test and control group, of 1,000 customer each. Following a test, the two groups have sales of say £11,000 for the test group and £10,000 for the control. How can i tell if the £1,000 ...
0
votes
0answers
10 views

optimization of engineering design algorithms

I want to do a small project about the use of optimization in engineering design using any real-world application. I have several topics. single/multi variable optimization algorythm non tradinoal ...
0
votes
0answers
7 views

help with formula for prediciting electrical consumption

I am trying to find a formula that I can use to find out what my consumption will be based on what the temperature might be, based on the comparison of what the consumption/temperature has been in the ...
0
votes
0answers
20 views

Ridge/lasso graph interpretation in R [duplicate]

Where I am in my analysis; I have concluded that I need to remove some of my variables (I have 13 of them atm) because my model suffers from multicollinearity. After this, I conduct ridge/lasso ...
0
votes
0answers
19 views

What is the marginal variance of the mean of $y$ if I only know the variance of the conditional mean of $y$?

Suppose an estimate for the conditional mean of $y$ given $x$ is $\hat{E}(y|x)$. Suppose the variance (or the variance estimate) of $\hat{E}(y|x)$ is known to be $V(\hat{E}(y|x))$ for all $x$. The ...
1
vote
0answers
10 views

Machine learning for product names

I have a machine learning challenge I may be over thinking. I have a set of 3.5 million products (not unique, there are multiple instances of each product). Each product has a "description" from it's ...
1
vote
0answers
16 views

Using non-stationary time series in cross-correlation analysis

I have modelled organism dynamics and abiotic factors time series in order to understand their seasonal oscillation and trend over time. Now I want to identify if there are any correlation between ...
2
votes
0answers
26 views

Estimates radically change when including Random Slopes in Multiple Logistic Regression

I am interested in the fixed effects of two within-subject experimental manipulations (i.e., Ambiguity 0 = No / 1 = Yes, and Uncertainty 0 = No / 1 = Yes) on a dichotomized variable (i.e., Punishment, ...
1
vote
0answers
10 views

Generalised least squares using QR decomposition

I know that the calculation of parameter values of a standard OLS can be made more efficient using a QR decomposition; i.e. if $X=QR$ and we are using the model $Y=X\beta+\epsilon$; Then it is true ...
1
vote
0answers
6 views

Basis vectors for categorical images

I have a sequence of categorical images. For a two category image, each image pixel can have one of two values. I would like to analyze these images using a technique like eigen images. The goal is to ...
1
vote
0answers
15 views

Reinforcement Learning partial derivative of loss function w.r.t. input of softmax

In the paper "Self-critical sequence training for image captioning" (link) on page 3 they define the loss function (of the parameters $\theta$) of an image captioning system as the negative expected ...
0
votes
0answers
11 views

variational lower bound confusion

In this blog describing variational inference under the section KL divergence and ELBO they mention that in the equation $$p(x) = \frac{w(x)}{Z}$$ we can substitute $w$ and $Z$ with: $$Z = p(x;\...
0
votes
1answer
30 views

Interpretation of Mean Square Error formula

This is a very basic question. I'm looking at a physical problem where one wants to estimate a parameter $\lambda$ of a system. Suppose I perform a measurement on the system. I call the (stochastic) ...
3
votes
1answer
27 views

Determining a Statistically Significant Result

I feel like this is an easy question if I just knew the right words to Google, but apparently I don't, so I'm sorry if it's been asked before. I'm simply looking to determine how long I need to ...
1
vote
0answers
20 views

R - Linear Regression with parameters constraint - contr.sum contrast

I am facing a problem with running a simple OLS regression with two categorical independent variable. I would like to impose that the sum of the coefficients referred to one variable (x in the ...
0
votes
0answers
7 views

Two correlated ordinal independent variables, several continuous dependent variables

I am currently struggling with a somewhat atypical analysis. People have been evaluating their cognitive state at two time periods – when they had attended school and at the present moment. Naturally, ...
0
votes
0answers
6 views

Conditional Exact Logistic Regression

I have paired data for two tests. I would like to say that Test A is more sensitive than Best B, but not sure if I'm using the correct methods or if my data support it. I know McNemar's Exact test can ...
0
votes
0answers
8 views

Analysing panel data - looking for hypothesized mediation and moderation effects

Good afternoon, I'd like to ask you for some help in finding a (hopefully citable) way of analyzing panel data when looking for mediation and moderation effects. Problem I have is that my measured ...
0
votes
0answers
8 views

Loss function for a risk neutral binary classification

For binary classification task, with samples labeled $y=0$ and $y=1$, a neural network has one output node with sigmoid activation function, producing predictions $\hat{y}\in(0;1)$. Is the following ...
2
votes
1answer
14 views

How to interpret chart generated by gbm.perf function?

I'm new to GBM.Can you help me to understand the interpretation of gbm.perf function? I used following code in R best.iter = gbm.perf(train, method="cv") & got ...
0
votes
0answers
14 views

How to interpret ARIMA (1,0,0) model?

I'm doing time series for my masters thesis, thus I need to interpret som ARIMA models. The data consist of number of recordings per night throughout the summer. I think I'm done with my coding now, ...
0
votes
0answers
20 views

How to explain why KNN has good classification performance (have example)

I have a good prediction results on KNN-DTW group classification (group labels are either 0 or 1). But I don't know how to explain how discriminative the 2 groups are. Then I tried k-means and tsne ...
0
votes
0answers
10 views

Comparing two NNLS models

I have two NNLS models: y=$\beta_1x_1 + \beta_2x_2$ y=$\beta_1x_1$ I want to compare these two models using ANOVA, but not sure how to apply it. I first tried to fit the models using python (...
0
votes
0answers
9 views

One-tailed Conover-Iman test?

I'm new to non-parametric statistics and want to do a post hoc analysis of some data after a Kruskal-Wallis test. I am using the implementation of the Conover-Iman test available in the scikit-...
0
votes
0answers
15 views

R glmer.nb : how building model with interaction between categorial variables

Before posting this, I made some research but I am very struggle with my modelling approach, so I will try to be clear in what I want to do with my data. I want to apologize if my questions are close ...
0
votes
0answers
14 views

How to interprete this Quantile Plot?

I did a multiple regression analysis for several production sites with energy consumption as dependent variable, and 2 other independent predictors (Floor space, production). When checking the ...
0
votes
0answers
5 views

Software that finds correlations between loosely dependent time-series?

I'm not sure if this is the right kind of question for this site, so please let me know :) I'm looking for a time series data analysis platform, so I can take a collection of time series at 15-...
0
votes
0answers
15 views

Pre-Master for a Master in Artificial Intelligence

I'm currently majoring in a bachelor of psychology and neuroscience, but I would like to go into a different field for my master: artificial intelligence. There are different programs on offer, but I ...
0
votes
0answers
8 views

How to create a model that will display a graph/table showing predicted units sold?

Goal: Create a model that will display a graph/table showing predicted units sold and then be able to use that to compare actual units sold during the season, eventually turning into an accumulated ...
0
votes
0answers
11 views

Global sensitivity Morris method - choice of delta and normalisation of the elementary effects

I have few questions regarding the Morris method (as decribed e.g. in Campolongo, Cariboni, Saltelli, Environmental Modelling & Software 22, 2007 or Wenthworth et al. J. Uncertainty Quantification ...
0
votes
0answers
11 views

k nearest neighbor for likert data

I have a data set which contains several variables. All these variables are catgorical variables. I want to use k nearst neighbour method. When I am using this technique do I need to convert the data ...
0
votes
0answers
10 views

Clustering HELP IMPORTANT [on hold]

I have a soil dataset that is unlabelled with 26 attributes like P,P-level....etc Example 7.55 L or H Or VH. I want to apply k-means to it....is it possible? Thanks in advance
0
votes
1answer
13 views

How to understand pLSA model Q function?

I know in EM algorithm M-step, it tries to solve $$ \operatorname{argmax}_{\theta} Q(\theta, \theta^{ \text{old}}) = \sum_z p(z|x; \theta^{ \text{old}}) \log p(x,z; \theta) $$ I also understand the ...
0
votes
0answers
9 views

Multiple regression with many possible predictors and with limited DV range

I have tabular data that records, on each row, a number of parameters to do with a patient's life-style, medication intake etc; plus the DV, that represents the severity of the symptom experienced in ...
0
votes
0answers
11 views

Fitting Probability Distribution to Failure Data with discrete, right censored stress

I'm a bit unfamiliar with survival analysis and I'm struggling to find examples of the particular problem I wish to tackle (which I don't think is particularly unique actually). Imagine I'm doing a ...
0
votes
0answers
9 views

Chi-square goodness-of-fit test

I am working with a categorical variable with 4 mutually exclusive classifications (CC, CD, DC and DD). I had counted how many times each classification is repeated. (for example, 33 CC, 40 CD, 50 DC ...
0
votes
2answers
20 views

In Linear regression is it possible to have same sign coefficients for dummies coming from the same variable?

So I have a categorical variable color which can take the values white, black, red. I created dummy variables for each of those ...
0
votes
1answer
11 views

Permutations, shuffling WITHIN but not BETWEEN groups [on hold]

In R, I need to make 100 repeat random permutations of group orders, keeping the composition and sizes of groups the same, but the order within the groups needs to be randomly shuffled (100 times) By ...
0
votes
0answers
9 views

pearson correlation between variables of two different data sets [on hold]

I have to find out the relationship between teachers resilience and students life skills development. the data of students is large and consists of 600 students of 29 classrooms clusters. each class ...
0
votes
1answer
13 views

Retuning hyperparameters of the baseline when comparing it with a new model

I have a baseline model which has certain hyperparameters to tune (it's actually a neural network, but I don't know if it's important in this context). I want to compare it with my own extension of ...
0
votes
1answer
24 views

Batch processing in a neural network

I am trying to understand how each batch is processed in a neural network. I understand that if we have a training set $X=\{x_1,...,x_{|X|}\}$ and we specify a batch size of $n$ than the neural ...
0
votes
0answers
11 views

How can I map a Gaussian vector according to an equation that has a spatial autocorrelation function?

I have the following function: $E(x,z)=30-0.5z+12.5\frac{e^{Y(x,z)}-e^{0.5}}{\sqrt{e^2-e}}$ I want to run some Monte Carlo simulations and at each simulation I have to generate values for $E$ at ...
1
vote
2answers
19 views

Interpretation very small standardized coefficient beta

In one of my studies I have results similar to the below: β=-0.0007 (95% CI: -0.0009, -0.0002), p=0.01 Since β is so small (but also the Confidence Interval (CI)), is this result still meaningful? ...
0
votes
0answers
7 views

standard error of the reference category of the outcome_ multinomial logistic regression

i am working with a multinomial logit model where i have a 6-category outcome and have a number of predictors of this outcome. i have fixed category 1 of the outcome as the reference in the model. i ...

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