All Questions
194,217
questions
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3
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Finding confidence interval given z-score and null hypothesis
I am working on a homework question and got stumped on this question.
Suppose researchers perform a large-sample test of a population proportion where the null hypothesis is that the population ...
1
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0
answers
14
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Arithmetic with normally-distributed variables
Suppose $x \sim \mathcal N(\mu_x,\sigma_x^2)$ and $y \sim \mathcal N(\mu_y,\sigma_y^2)$ are random variables, and suppose $\mu_y$ is large compared to $\sigma_y$. I want to know about
$$
z=\frac{x}{y^...
- 1,078
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0
answers
3
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Could someone help me with R code to estimate the Value-at-Risk using the hierarchical Archimedean copula approach?
To estimate the Value-at-Risk of a two-dimensional portfolio (d=2) by the archimedean copula approach, the process can be for example :
x<-mvdc(archmCopula(family="gumbel",param=3),c(&...
- 21
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0
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5
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Can I use one-way ANOVA for two and for three groups in order to maintain consistency across different sample types?
TLDR: Some of my larger dataset has two levels, while some has three levels. Is it appropriate to test everything using one-way ANOVAs or should I do some as t-tests and some as ANOVAs (Welch's for ...
1
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0
answers
5
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Please, could someone help me with the R codes of goodness-of-fit tests on hierarchical archimedean copulas?
My question is to know on the one hand which methods are used for goodness-of-fit tests in the case of hierarchical archimedean copulas(dimension greater than two), and on the other hand which R code ...
- 21
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0
answers
2
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Hopfield nets and SDM: clarifying associative memories vs function approximators
Both Hopfield networks and Sparse Distributed Memory (its generalization) are biologically plausible associative memory models that can be implemented as neural nets (insofar as being able to write ...
- 153
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0
answers
12
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How to handle independent variable in regression where no relationship exists between samples
I would like to use a multinomial logistic regression to get win probabilities for each of the 5 horses that participate in any given race using each horses previous average speed.
...
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2
votes
1
answer
27
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How do I account for total effect of a variable in a regression?
Suppose I want to understand the influence of gender $X$ on wage $Y$, so I use the linear regression model
$$
Y=\beta X + \varepsilon
$$
We might want to be conscious of omitted variable bias, so we ...
- 21
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votes
0
answers
17
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Hazard function and survival analysis
I have a function $\lambda(t)$ which returns the instant probability of dying at a time $t$. I'd like to compute the function $F(t)$ which returns the probability of being dead at a certain time $t$.
...
- 113
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0
answers
11
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How to add categorical variable to continuous when doing Linear Regression in Python?
If I have independent cts variables [x1, x2, x3] and categorical variable [x4] which can be categorized into [x4_1, x4_2] for dummy variable 0/1
If I fit linear regression in sklearn
it will give me ...
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0
answers
3
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Recurrent event analysis: What approach to choose?
I am trying to examine if the interval between recurrent suicide episodes becomes shorter over the course of repeated incidents. My data is in long format with each participant occupying multiple rows ...
- 1
3
votes
2
answers
25
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Interpreting log-log regression with log(1+x) as independent variable
Is interpreting log-log regression with log(1+x) as independent variable the same as having log(x) as independent variable? 1% increase in x results in beta% change in y?
What is x has both negative ...
- 31
0
votes
1
answer
14
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Is "vanilla" random forest regression appropriate when dependent variable is a rate (i.e. per 100 people)?
To add a little more context, I am working with a dataset from which I want to predict the population-normalized count of emergency department visits on county level, with 50+ independent variables. ...
- 61
1
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0
answers
5
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Can you average ICC values for Intra-rater reliability?
I am using ICCs to test the inter- and intra-rater reliability for a body condition scoring system. I have two different groups of evaluators: specialists and students. I would like to evaluate the ...
- 11
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0
answers
5
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Three-levels Meta-Analyses: Within-study moderators and correction for publication bias?
I'm conducting a three-level meta-analysis on correlations using the {metafor} package on R.
I'm quite a newbie when it comes to three-level meta-analyses, so I have two doubts.
1) From each study, I ...
- 1
0
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0
answers
12
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How to compare two time series with a gam?
I recently got comments back from a review who suggested I use a gam to compare two time series to see what the trends are and if the two time series are different from one another. I'm am trying to ...
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1
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0
answers
15
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How can any sample be drawn from a continuous distribution? [duplicate]
Since the probability of a continuous variable $X$ assume any particular value is always zero, how can any sample be obtained from such distribution? How can we obtain, e.g., the set of observations $\...
- 41
1
vote
1
answer
16
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Urn problem (draw two balls of different colours with replacement)
e.g. 3 white balls and 7 black balls.
Prove that the probability to draw two different coloured balls is 0.42
I get the intuition, but can't formally explain the probability.
- 11
0
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0
answers
6
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What is an alternative to Chi-Square for observed vs. expected variance suitable for repeated measures?
I want to test for individual-level side preference of a behaviour during an experiment, and found a way to do this using a chi-square test that uses the number of right (or left) turns out of the ten ...
- 11
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votes
0
answers
8
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Caret ordinalRF error when using classProbs= TRUE: attempt to set 'colnames' on an object with less than two dimensions [closed]
I am trying to train a random forest with caret.
All the variables in my dataset (here the link to it) are categorical, and many of them ordered, including the dependent variable. So I added ...
- 101
1
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0
answers
16
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Using ML model and decision tree to create a new risk classification
The idea of this project was to use a Machine Learning model to find the best variables to include in a decision tree algorithm. After evaluating with caret a number of different models I found the ...
- 11
0
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0
answers
13
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How to calculate the accuracy of a yes/no Monte Carlo simulation such as "throwing stones in a pond"? [duplicate]
I have a simulation that returns "yes" or "no" for each iteration, and I measure the average number of "hits" over many iterations to estimate the likelihood of "yes&...
- 547
1
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0
answers
9
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Methods for estimating the future evolution of these graphs
A friend and I were looking at the following graphs and discussing their possible future evolution:
The blue graph is inflation while the orange one is interest rate. Neither of us is particularly ...
- 111
1
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0
answers
5
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Temperature Lag calculation
I am working on a data science project on an industrial machine. This machine has two heating infrastructures. (fuel and electricity). It uses these two heatings at the same time, and I am trying ...
- 21
0
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0
answers
4
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Evaluating the posterior probability that the restricted mean survival time (RMST) exceeds some efficacy threshold $\theta$
This is related to a previous question I've asked here. Suppose we have survival data of the form $\{(T_i,C_i,\delta_i),i=1,\ldots n\}$ where
$T_i$'s with common pdf $f(\cdot)$ and survival function $...
- 1,570
0
votes
2
answers
36
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Why use normality tests if we have goodness-of-fit tests?
What are the reason/s to use a normality test (e.gr., Shapiro-Wilk, Jarque-Bera) instead of a goodness-of-fit test to a normal distribution for some data we want to check for normality?
- 179
1
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0
answers
15
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Help with terminology & methodology for a hierarchical (& imbalanced) classification problem
I have a dataset that I am not sure how to analyze, or at least I am not sure of the terms to read up on. I have 25 groups. Each group belongs to one of 3 locations. Each group consists of multiple ...
- 11
1
vote
1
answer
14
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Image classification using Binary Cross Entropy but with only training examples for one of the classes e.g. class 1 VS anything else
I am training a 'specialist network' to reconstruct images of an object using a Variational Autoencoder (VAE). The training set (~15000 images) is of a single object in multiple poses.
I also want ...
- 11
0
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0
answers
9
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LSTM architecture for forecasting amplitude varying univariate-timeseries
Hi I am wondering if someone knows what a good LSTM architecture for amplitude varying univariate time series.
I used a very simple LSTM network (1 lstm layer with 100 neuron's and FCC layer with a ...
- 111
1
vote
0
answers
13
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Normality assumption of structural shocks in Vector Autoregression model
I’m currently working on forecasting yield curve evolution over time using a state space model where the transition dynamics are described using a vector autoregressive model of order 1. This model ...
- 11
0
votes
0
answers
23
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How to determine the number of strata from stratified sampling? Any rule of thumb?
I have a continuous variable (proxy for difficulty) that I would like to discretize for stratified sampling. My sampling approach is equal allocation (I will choose an equal proportion of samples per ...
- 33
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votes
1
answer
12
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Building model for SEM: the problematic of highly correlated variables (SEM + Covariance)
I have recently come across articles suggesting we should avoid conducting SEM when variables are highly correlated.
I have a model in which X1 and X2 predicts Y through M1 and M2. Which gives me the ...
- 1
0
votes
0
answers
4
views
Using the Dunn test to get the CLD grouping for the Skillings-Mack test
I have a set of phenotypic data collected from 9 different assays of a set of different plants. Each plant was assayed at least one time, but each individual assay had a different set of plants. So ...
- 1
1
vote
2
answers
40
views
Chi-Square Difference Test for Nested Models with a Continuous Outcome
Apologies if this is a very basic question - I'm still definitely a beginner when it comes to statistical tests. I understand that chi-square tests are conducted to determine the relationship between ...
- 11
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0
answers
7
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Matrix Factorization for Recommendation System vs just calculating Conditional Probabilities
I have a matrix factorization model (using Lightfm, without user-features) to recommend items to users, based on a user-item matrix.
Context
A particular recommendation stuck out to me as curious, ...
- 283
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0
answers
13
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Techniques Used for DeepFake and Its Corresponding Research Field
I'm a beginner in image generative models, I'm trying to do some work similar to DeepFake, therefore I would like to find out first what techniques DeepFake use to generate the fake videos. Do they ...
- 1,643
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votes
0
answers
8
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Are gaussian mixture models for clustering robust to data sparsity?
I would like to cluster customers based on their product usage data (20-40 products/dimensions) on the same scale. Overall, the data is reasonably log-normally distributed for all products (the ...
- 101
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0
answers
6
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For a CNN Neural Network, why do we need to specify the number of nodes in the Conv2D function in Keras? [closed]
As I understand, in CNN, we are only doing dot product calculation on the image in the convolution layer. Below is an example of convolution code.
...
- 111
0
votes
1
answer
9
views
Why not perform weight decay on layernorm/embedding?
I am learning the code of minGPT. In the function, the author excluded layernorm and embedding layer from experiencing weight decay and I want to know the reasons. Besides, what about batchnorm?
- 71
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votes
0
answers
26
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How do I handle basic time series prediction? [closed]
I have data like:
may 2019 value=74 cost centre=c1 and I want it to predict values for cost centres. The data is monthly and I only have a few years worth (max 48 ...
- 133
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votes
0
answers
10
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Average VIF after dummy variables [duplicate]
I have classified (label encoding) independent variables. To calculate VIF, I converted them to dummy variables. When I calculate VIF for dummy variables, there are VIF values for each class of an ...
- 1
2
votes
1
answer
54
views
How to get most likely value with confidence interval or expected value from a set of observations
lets say I have a set of values (R-code below for creating a vector)
...
- 151
2
votes
0
answers
13
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Testing for a common intersection of p linear regression lines
I'm trying to derive a test for testing if p regression lines have a common point of intersection.
Let the p regression lines intersect at a point $(x_0,y_0)$. We are to test: $H_0: a_1+b_1*x_0 = a_2+...
- 113
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0
answers
10
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Does Class Imbalance in Audio Classification Occur When There's an Imbalance in Mean Audio Durations or in Number of Instances of the Classes?
I'm currently working on a speech emotion recognition task, and I was curious to know whether my dataset is imbalanced or not.
The value counts for each class are roughly uniform except for one class ...
0
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0
answers
6
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Question about Control charts and calculating the X-bar limits using the R and S
The following data originate from a standard sample used for monitoring the accuracy of an equipment that determines protein content at an analysis laboratory. The standard has a protein content of 3....
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2
votes
1
answer
33
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Showing that the restricted mean survival time (RMST) of iid $\mathsf{exp}(\lambda)$ survival time random variables is decreasing in $\lambda$
I would like to show that $\frac{1-\exp(-\lambda\tau)}{\lambda}$ is a decreasing function of $\lambda$ where $\lambda,\tau>0$.
Motivation: Suppose we have iid continuous survival time random ...
- 1,570
0
votes
0
answers
17
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Monte Carlo simulation or Bootstrap for determining sample L-moments estimates
I'm trying to estimate the sample L-moments of stations from the Annual Maximum Series of precipitation. The book by Hosking (1986a, 1990) recommend using Monte Carlo simulation in generating ...
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-1
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0
answers
18
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Linear Regression Using QR Decomposition Intuition
I'm trying to understand part of the QR decomposition algorithm that uses the householder rotations to find Q and R. I am familiar with the concept of transformation matrices and their use in ...
- 99
0
votes
0
answers
17
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Use Large Dataset to Predict Missing Features in Smaller Dataset [closed]
I'm am in the process of learning statistical modeling and have a general question. I have two related datasets. One of them is quite large, both in the number of observations and the number of ...
- 101
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0
answers
10
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How many components of a gaussian mixtures do I need to match moments up to the $r$-th order?
Suppose I have a ($k$-dimensional) random variable $X \sim D$ and I want to find a Gaussian Mixture $GM \sim \sum_{i=1}^C \pi_i \mathcal{N}(\mu_i, \Sigma_i)$ such that the moments of order $r'$, for $...
- 1