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Cross Validated : Recent Questions and Answers (Page 9)

Find answers to your questions about Cross Validated or help others by answering their Cross Validated questions.

What's wrong in this derivation of back-propagation errors?

I'm trying to find a rigorous derivation for the backpropagation algorithm, and I've gotten myself into something of a confusion. The confusion comes from when and why people transpose the...

Asked on 12/27/2021

1 answer

How does probability of default evolve over time?

Say I have a probability of default of 0.02 (which is annual so over next year) for a certain client. Then say this client takes out a 180 day loan,...

Asked on 12/27/2021 by mathella

1 answer

Random effects not appearing for some levels in lmer model - Why would that be?

Here's my code in R but I unfortunately can't share my data, and I can't reproduce it by randomly creating a data set. I can say that the data...

Asked on 12/25/2021

1 answer

Logistic regression with lasso versus PCA?

Logistic regression with lasso versus PCA?Got asked this question in an interview. I know the main difference is that Lasso is a regularization technique (adding vars to minimize effect of...

Asked on 12/25/2021 by Manas

2 answer

Is spurious regression a problem for lasso and similar techniques?

I was toying with R to see how the number of variables might affect spurious regression. Suppose that we have an $I(1)$ vector $y$ and a matrix ...

Asked on 12/25/2021 by badmax

1 answer

Dealing with singular fit in mixed models

Let's say we have a model mod <- Y ~ X*Condition + (X*Condition|subject)# Y = logit variable # X = continuous variable # Condition = values A...

Asked on 12/25/2021 by User33268

2 answer

groups, levels and denominator dof in mixed effect models

I am trying very hard (I am not a statistician) to understand the concepts of "groups" and "levels" in mixed effect models. In particular, I am trying to understand this...

Asked on 12/25/2021

1 answer

p-value random effect in glmer() in lme4 package

I know that in order to test whether a random effect has a significant impact on a model it's necessary to sequentially remove one random effect at a time and...

Asked on 12/25/2021 by ribelles

1 answer

Question about the structures and conditions of validity of the mixed-effect model

In class we are told to be very careful when using mixed models and to use the simplest models, to avoid talking nonsense. I posted questions previously about this but...

Asked on 12/25/2021

1 answer

Increasing multicollinearity in multilevel/hierarchical modeling?

I have a linear model with response variable $textbf{y}$ and explanatory variable matrix $textbf{X}$ for which coefficients $textbf{b}$ are physically meaningful and worth estimating: begin{equation}textbf{y}...

Asked on 12/25/2021

1 answer

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