Top new questions this week:
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I used to say that OLS is an estimation technique and should never be confused with the type of model on which it is applied. Thus a phrase like “I have an OLS model” would not make sense to …
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This is a question I have been trying to look into. Consider Linear Regression – depending on how the model parameters (i.e. “beta” regression coefficients) are estimated (e.g. Ordinary …
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Given $X_{1},\dots,X_{n}$ i.i.d. $\sim N(μ,σ^{2})$, it’s known that a confidence interval for the variance with $1-\alpha$ confidence is as it follows $$\sigma^2\in\Biggl(\frac{(n-1)S_{n}^{2}}{\chi^{2}…
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For example, we say that an estimator is unbiased if the expected value of the estimator is the true value of the parameter we’re trying to estimate. However, if we already know the true value of the …
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Let’s say I want to perform a logistic regression (binomial) as : X ~ P1 + P2 + P3 + P4 + P5 where X is binary variable (0 or 1) and P1, P2, P3, P4, P5 are …
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I am trying to understand what variance is, I already know the “official” definition “Variance is the average squared deviations from the mean” But I am trying to give it a visual …
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I note that the lognormal distribution approaches a normal for a small coefficient of variation, but I’m having a hard time showing this mathematically. Can someone help?
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Greatest hits from previous weeks:
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I want to know how to check a data set for normality in Excel, just to verify that the requirements for using a t-test are being met. For the right tail, is it appropriate to just calculate a mean …
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I understand that the basic definition of endogeneity is that $$ X’\epsilon=0 $$ is not satisfied, but what does this mean in a real world sense? I read the Wikipedia article, with the supply and …
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What’s the similarities and differences between these 3 methods: Bagging, Boosting, Stacking? Which is the best one? And why? Can you give me an example for each?
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Data analysis cartoons can be useful for many reasons: they help communicate; they show that quantitative people have a sense of humor too; they can instigate good teaching moments; and they can help …
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When training a neural network, what difference does it make to set: batch size to $a$ and number of iterations to $b$ vs. batch size to $c$ and number of iterations to $d$ where $ ab = cd $? To …
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Is there a standard and accepted method for selecting the number of layers, and the number of nodes in each layer, in a feed-forward neural network? I’m interested in automated ways of building neural …
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I got this question during an interview with Amazon: 50% of all people who receive a first interview receive a second interview 95% of your friends that got a second interview felt they had a good …
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Can you answer these questions?
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According to page 33 of Targeted Learning: Causal Inference for Observational and Experimental Data written by Mark J. van der Laan, when the distribution of exogenous variable $U$ is such that, for …
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If we have two random variables $X$ and $Y$, then $\text{corr}(X,Y)=\dfrac{ \text{cov}(X,Y) }{ \sqrt{ \text{var}(X)\text{var}(Y) } }$. This correlation will not be defined if either variable has an …
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In my study, I want to investigate the influence of job skills on psychology. Job skill, as an exogenous latent variable, is composed of 3 categorical variables (V1, V2 and V3 here). Psychology, as an …
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