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1500 questions
47
votes
5 answers
Understanding regressions - the role of the model
How can a regression model be any use if you don't know the function you are trying to get the parameters for?
I saw a piece of research that said that mothers who breast fed their children were less likely to suffer diabetes in later life. The…
Jonathan Andrews
- 471
47
votes
4 answers
What is an instrumental variable?
Instrumental variables are becoming increasingly common in applied economics and statistics. For the uninitiated, can we have some non-technical answers to the following questions:
What is an instrumental variable?
When would one want to employ an…
Graham Cookson
- 8,061
47
votes
2 answers
How can I test whether a random effect is significant?
I am trying to understand when to use a random effect and when it is unnecessary. Ive been told a rule of thumb is if you have 4 or more groups/individuals which I do (15 individual moose). Some of those moose were experimented on 2 or 3 times for…
Kerry
- 1,219
47
votes
6 answers
How seriously should I think about the different philosophies of statistics?
I've just finished a module where we covered the different approaches to statistical problems – mainly Bayesian vs frequentist. The lecturer also announced that she is a frequentist. We covered some paradoxes and generally the quirks of each…
DerrYe
- 423
47
votes
3 answers
Test for bimodal distribution
I wonder if there is any statistical test to "test" the significance of a bimodal distribution. I mean, How much my data meets the bimodal distribution or not? If so, is there any test in the R program?
Pauloc
- 653
47
votes
5 answers
Negative values for AICc (corrected Akaike Information Criterion)
I have calculated AIC and AICc to compare two general linear mixed models; The AICs are positive with model 1 having a lower AIC than model 2. However, the values for AICc are both negative (model 1 is still < model 2). Is it valid to use and…
Freya Harrison
- 3,412
47
votes
4 answers
Is LSTM (Long Short-Term Memory) dead?
From my own experience, LSTM has a long training time, and does not improve performance significantly in many real world tasks.
To make the question more specific, I want to ask when LSTM will work better than other deep NN (may be with real world…
Haitao Du
- 36,852
- 25
- 145
- 242
47
votes
2 answers
How well can multiple regression really "control for" covariates?
We’re all familiar with observational studies that attempt to establish a causal link between a nonrandomized predictor X and an outcome by including every imaginable potential confounder in a multiple regression model. By thus “controlling for” all…
half-pass
- 3,740
47
votes
3 answers
Empirical relationship between mean, median and mode
For a unimodal distribution that is moderately skewed, we have the following empirical relationship between the mean, median and mode:
$$
\text{(Mean - Mode)}\sim 3\,\text{(Mean - Median)}
$$
How was this relationship derived?
Did Karl Pearson…
Sara
- 1,487
47
votes
1 answer
Computing Cohen's Kappa variance (and standard errors)
The Kappa ($\kappa$) statistic was introduced in 1960 by Cohen [1] to measure agreement between two raters. Its variance, however, had been a source of contradictions for quite a some time.
My question is about which is the best variance…
Cesar
- 1,004
47
votes
8 answers
How to do community detection in a weighted social network/graph?
I'm wondering if someone could suggest what are good starting points when it comes to performing community detection/graph partitioning/clustering on a graph that has weighted, undirected edges. The graph in question has approximately 3 million…
laramichaels
- 1,139
47
votes
8 answers
What is the reason why we use natural logarithm (ln) rather than log to base 10 in specifying function in econometrics?
What is the reason why we use natural logarithm (ln) rather than log to base 10 in specifying functions in econometrics?
ritho
47
votes
2 answers
Quantile regression: Loss function
I am trying to understand the quantile regression, but one thing that makes me suffer is the choice of the loss function.
$\rho_\tau(u) = u(\tau-1_{\{u<0\}})$
I know that the minimum of the expectation of $\rho_\tau(y-u)$ is equal to the…
CDO
- 573
47
votes
6 answers
Does the reciprocal of a probability represent anything?
I was wondering if the reciprocal of P(X = 1) represents anything in particular?
A. Fleming
- 571
47
votes
1 answer
Why are non zero-centered activation functions a problem in backpropagation?
I read here the following:
Sigmoid outputs are not zero-centered. This is undesirable since neurons in later layers of processing in a Neural Network (more on
this soon) would be receiving data that is not zero-centered. This has
implications…
Amelio Vazquez-Reina
- 19,346