# All Questions

136,547 questions
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### Problemas con decimales [on hold]

Tengo un data.frame con datos de valores grandes en €. Existen tres problemas: 1º No me reconoce el "€" como valor, en su defecto me pone â‚¬. Lo he omitido con gsub("â‚¬", "", nombrevariable) 2º ...
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### A little help with probability calculation [on hold]

i have a question, if we know P(A) and P(B),how can we calculate the $P(A) \bigcap P(B)$? for example let say P(A)=2/3 and P(B)=1/6
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### How to deal with circular causality

Often in time series and panels, the "dependent" and "causal" variable don't share purely that relationship. There is a fair bit of reverse causality as well. ,e.g. x causes y, but then either y ...
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### Conditional Independence

I have a joint probability, which factors as follows: $P(A,B,C,D) = P(A,B) \cdot P(C|A) \cdot P(D|B)$ So I know that $C$ and $D$ are independent given $P(A, B)$ right? I want to infer $P(A,B|C,D)$....
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### Why we get different important factors when performing logistic regression and decision tree?

Why we get different important factors when performing logistic regression and decision tree? When I select features, I perform logistic regression and decision tree separately and wanna see the ...
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### In survival analysis, when should we use fully parametric models over semi-parametric ones?

This question is the counterpoint of the other question In survival analysis, why do we use semi-parametric models (Cox proportional hazards) instead of fully parametric models? Indeed, it clearly ...
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### Saving plots in folder in R without overlapping [migrated]

I am currently running my own program in R programming. And I am struggling to figure out the solution for my problem. I have two for loops and I m saving the plots into a folder, first for loop have ...
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### How to predict how many customers are going to purchase based on population purchase frequency?

I am trying to calculate a metric "frequency of purchase of a customer" to determine when I would expect a customer to then purchase an item next. Say, the distribution of my customer base looks like ...
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### Parallel analysis with rotated data

I am trying to do Factor analysis with varimax rotation for my data using R psych package. To determine number of factors I use R paran package. The problem I see is that eigenvalues produced by ...
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### Log transformed data [on hold]

When you log transform data what is being tested on the original scale of the data? And why can we use our log transformed data to answer our scientific question? We are looking at data comparing ...
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### Are there any exisitng scales (e.g. in a paper) for measuring perception of a short team task (or general tasks) in a questionnaire?

The task in concern is a one-time 10-20 second game to be played as a team. Scale can be Likert scale or metric scale (if possible). Perception is e.g. whether the game is boring/interesting, ...
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### When do these two definitions of KL-divergence match?

Suppose $P$ and $Q$ are two distributions on a space ${\cal H}$ (could be a subset of an infinite dimensional function space) with p.d.fs denoted by the same letter then one can define the $KL$ ...
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### Deriving the values of the range around the mean value

This is part of a bigger quantitative reasoning assignment I was working on. My understanding here is that the upper bound and lower bound of the ranges for each of the exercises should be reflected ...
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### Should loss function be defined over output or parameters?

In machine learning loss is usually defined over the actual output and the predicted output $L(Y,\hat{Y}(X))$, while in statistics it's defined in the parameter space $L(\theta,\hat{\theta}(X))$. Why? ...
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### Create dummy variables out of a text variable?

I'm trying to create dummy variables for a variable that has text data in rows. Data in 1st row is: ...
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### Sample size (CI 95%)

I have two groups (treatment and placebo) and for each group I have the 95% CI mean calculated as per here. I want to do the same for calculating the 95% sample size as per table 11 of this paper: ...
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### fitting non-normal multivariate distributions in R

I have many (n=317,823) observations on two variables. I want to fit a bivariate distribution to my observations, in order to identify descriptive features of the distribution (quantiles). However, my ...
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### How to get the Standard Deviation based on the sample [on hold]

The situation is I have 96 sets of paper, 4 questions on every paper and categorized into 5 categories.Every options consisting marks of 0,1,2,3,4. What's the formula to calculate the Standard ...
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### A variance of how much is acceptable for a column before we can use it for modelling?

I am trying to create a classification model. While pre-processing the data. I look at the variance in each column. This is the amount of variance in each column. I am confused on which all columns ...
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### interpreting rank difference trend

I am doing some research utilizing popularity ranks in Internet data. I've been able to model the rank data using Zipf Law effectively. I am interested in understanding how the rank changes, as well. ...
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### State whether the statement are True or False for statistics modeling questions? And explain the reasoning [on hold]

For the first two statement, I think they are true, but I don't know how to explain them. For the last one I'm not sure whether it is true. The change deviance can be compared against chi-square to ...
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### About using a neural network to train another neural network (on the same problem)

While experimenting with OpenAI gym to play a bit with reinforcement learning, I ended with using an approach that I can't exactly say what type of paradigm of training is, and I'd like to get your ...
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### Long data format for Mixed linear modeling

I have a data set from an experiment with two conditions: a control condition, and a testing condition. It's an experiment performed in pairs. Each condition was undertaken by 20 pairs of subjects (...
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### Uniform distribution of p-values

I have a question regarding the distribution of p-values. http://varianceexplained.org/statistics/interpreting-pvalue-histogram/ In this article it says that under the null hypothesis the ...
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### T Test or Chi Square?

There are 2 variables, City and No Of Matches won. Variables: 1City Sydney Canberra 2No Of Matches Won? Sydney: 200 out of 300 Canberra: 210 out of 300 Question: Is team Canberra ...
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### How to analyze EEG time-frequency data in a factorial design

I am trying to find the best strategy to analyze a set of EEG time-frequency data from 24 subjects, using 64 electrodes. This is an exploratory study as I have no a-priori hypothesis on where or when ...
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### Feature engineering for verb\non-verb classification

Suppose we have data of X = words, and for each word we have a label indicating whether the word is a verb or a non-verb. So, y = labels. Assuming we can build all the unigrams and bigrams of each of ...
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### Not testing for stationarity in a panel data set

Currently, I am analyzing a panel data set (different individuals over time) using panel data models with the lagged dependent variable as an explanatory variable. In this case the stationarity ...
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### Finding significant explanatory values with unregularized logistic regression?

So i'm working currently with a colleague on a classification problem where both of us have different approaches. So i try to find the most important features through standard L1 regularization and he ...
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### How to calculate bias and variance of Stacking model (a machine learning model)?

I'm doing bias-variance decomposition of Stacking model in regression case. The 1st-level learners include Random Forest, Extra-Trees and Gradient Boosting; then 2nd-level learner is Gradient Boosting....
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### Are CNNs just an efficiency shortcut to Dense Layers?

I'm reading up on Convolutions in neural nets, and they seem like a neat and efficient way of finding "features" in the input. But am I right in thinking that a high enough number of layers and ...