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# Cross Validated : Recent Questions and Answers (Page 5)

## Specifying and extracting random intercepts and slopes from GAMM using bam in mgcv

I have two questions about how to specify random effects structures in mgcv using bam. I'm using bam because I have a large data set (~15,000 data points) that consists...

## Where is the proof that replacing missing lagged values with zero in Arellano-Bond like estimators is a valid approach?

If I use lagged values ($k, k geq 2$) as instruments to estimate an $AR(1)$ model (to take into account that the lagged value is endogenous),there's the...

Asked on 01/01/2022 by Federico Tedeschi

## Is there any anova-like approach for calculating contingency tables across multiple levels within a factor

I want to compare success rates across a large number of different levels within a third factor to detect if there are statistically significant differences for at least one of...

## How to extend Plackett-Burman design to further explore the interactions?

My situation is as follows: I have built a 2-level Plackett-Burman design with 10 factors (some are actual 0/1-variables, the others are numeric and I used the minimum and the...

## What is the difference between RMSE and SEP

I would like to understand the difference between Root Mean Squared Error and the Standard Prediction Error. The SEP formula is simillar to the RMSE, but with an aditional term...

Asked on 01/01/2022 by Tiago Dias

## How to choose an optimizer for your Neural Network?

My question boils down to this : Which optimizer should I use to train my neural network. I understand this question depends on the problem. However, for instance it seems...

## Box-Cox data transformation to enable linear regression

I am performing multiple linear regression to predict a score (dependent variable) from multiple categorical variables. My dependent variable has skewed distribution with a large number of zero values but...

## Why isn't simulation showing that ridge regression better than linear model

I am learning about ridge regression. I was under the impression that ridge regression is valuable because it provides better out of sample predictive accuracy than standard linear models. For...

## Does the t statistic have uses unrelated to hypothesis testing?

Are there non-hypothesis testing uses for Student's t statistic?...

## survival analysis using unbalanced sample

I am new to survival analysis. Below is my data with very unbalanced sample size (treat group has 2 samples with 1 event, 1 censored and control group has 700+...