# Tagged Questions

Causal inference tries to quantify the effect of a change in $X$ on $Y$ whilst holding constant or eliminating all other relevant factors which might influence this relationship.

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### Estimate a curvilinear relationship (inverted U shaped) using difference-in-differences estimator

If I want to estimate a potential curvilinear relationship (inverted U shaped) between X and Y, whether it is possible to use difference-in-differences regression (suppose I can explore variations in ...
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### Fixed effects in regression discontinuity design

I want to do an RDD type analysis to know the impact of an intervention (a single dummy variable) on an outcome variable. I have several 'boundaries' (which are actually different geographical ...
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### How do I estimate sensitivity of two outcomes variables from a difference-in-differences setup?

Say I estimate the following multi-period DID equations separately: $\frac{Y^1_{it}}{A_{it}} = \alpha^1_i + \alpha^1_t + \tau^1 D_i\times Post + \beta^1C_{it} + \epsilon^1_{it}$ ...
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### Prior on effect of treatment using CausalImpact library in R

I'm using the package causalImpact in R to estimate the causal effect of an intervention in a time series. However, I have strong prior information that the effect can't be negative. How can I encode ...
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### decomposing average treatment effect

Suppose I estimate a difference-in-difference (DID) model on some outcome variable Y, and say I found a statistically significant average treatment effect (ATE). Using the same DID model on another ...
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### Durbin-Watson: test exogeneity

I have a time series for which I have built a linear regression, say $Y(t)=\beta X(t)$. A regression implies that $Y$ is actually a function of $X$ (that is, $Y(X)$), but not the other way around ...
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### Experimental treatments assigned via email how best estimate average treatment effects?

A growing number of social experiments are conducted outside of the laboratory, and by assigning the treatment condition through emails (e.g., often the content of the email is the intervention ...
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### Methods of Treatment Effect Heterogeneity Estimation (Observation Data)

Given observational data, where a "treatment" is chosen by the unit of observation or not, are there any standard methods of ascertaining not just if the treatment has effect overall (ATT), but ...
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### Understanding the direction & strength of a correlation, & causal status, from a chi-squared test

I am analyzing Stack Overflow Posts. So I have a database with 1000000 questions, their current score (upvote or downvote) and a flag, that there is a source code part in the question (or not). So I ...
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### Robust Coefficients For Differences in Differences

I have a panel data set which I am looking to analyze for relationships/causality using the OLS differences-in-differences method. The panel data includes multiple observations over time for various ...
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### Causal Trees to Estimate Heterogenous Treatment Effects: Transformed Outcomes [Machine Learning in Python]

I am interested in using off-the-shelf tools like scikit-learn for Python to implement the Athey-Imbens recommendation for estimating treatment effect ...
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### fixed effects question

I am analyzing survey respondent data. Respondents are nested within regions and are surveyed 4 times. Over the 4 time periods, different regions undergo a policy change (go from 0 to 1) randomly (or ...
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### why are these uplift estimates different?

I recently stumbled upon an ODSC presentation: Machine Learning Based Personalization Using Uplift Analytics: Examples and Applications Uplift wherein two methods for "uplift" estimation are provided: ...
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### CausalImpact - Should I use more than one control?

In the intro document (https://google.github.io/CausalImpact/CausalImpact.html) it suggests that using one predictor is not ideal. Am I current in understand that they mean one control? If so, should ...
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### Challenging Propensity Score/Causal Inference Problem

I am reaching out to the Cross-Validated statistical community seeking suggestions on a challenging problem on which I'm working. I've been asked to look into a problem related to electronic ...
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### Causality studies on observational data: DID with 2SLS to compliment Rubin causal model

A study with observational data has treatment and control group but the assignment is not randomised: some chose to be in the treament, some otherwise. But the choice had been made before the ...
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### How to incorporate characteristics of the object of outcome variables as predictors in model

I'm working with survey data for a social science research topic. The particulars aren't super important, so I'll use a simplified version to make it easier to understand what I'm trying to do. I say ...
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### Using spike-slab to fit log-link GLM Gamma

I am attempting to model the causal impact (using CausalImpact package in R) of a know discrete event on the change in medical expenditures. I have 12 pre and 6 post period observations and upwards of ...
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### Variables with low coefficients/high p-values in multiple linear regression highly correlated to significant predictors

This is possibly a very naive question: I am watching Hastie and Tibshiranie's class ("Introduction to Statistical Learning"), and at the end of this lecture, Tibshirani gives example of a multiple ...
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### CausalImpact - Is pre-processing of covariates required?

I'm using the CausalImpact to evaluate the effect of a programme. My covariates are seasonal and I wonder whether I need to deseasonalise/ detrend the regressors before using the R package? Hal ...
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### Representing interaction effects in directed acyclic graphs

Directed acyclic graphs (DAGs; e.g. Greenland, et al, 1999) are a part of a formalism of causal inference from the contrafactual interpretation of causality camp. In these graphs the presence of an ...
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### CausalImpact on single time series

Today I have tried to play a little with CausalImpact R-package https://google.github.io/CausalImpact/CausalImpact.html (Brodersen et al. 2015) to explore the impact of some decissions in a sales data ...
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### How can I analyze / compare point-of-sales data between stores with different product offerings?

Let's say I have two stores, A and B, and let's say I have two products in the same department: product 1 and product 2. Let store B have product 2 which store A doesn't have, both stores have product ...
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### Modeling complex mechanism with regression (or similar method)

There are six variables A, A', B, C, D, and D' and they are related as shown in the figure below. I want to know the effect of A on C through B. I firstly thought to use 2SLS, but since A and C are ...
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### Questions about the paper “Inferring causal impact using Bayesian structural time series models”

I am simulating this model in the paper Brodersen et al. (2015) and found I have difficulties on figuring out how to choose the starting point of Bayesian inference. To be explicit, to my ...
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### How to test whether it is valid causal inference

definition of average causal effect $$ACE = E(C_1) - E(C_0)$$ $$ACE = E(Y|X=1) - E(Y|X=0)$$ given the condition that $$X \bot (Y(0), Y(1))$$ So if I have a regression ...
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### Regression discontinuity design with multiple cutoffs

When we have an RD with multiple cutoffs, and we pool all observations and estimate the treatment effect across cutoffs, what does the pooled estimate identify? I have found one paper using a RDD ...
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### What is the best way to visualize difference-in-differences (multi-period) regression?

What's the best way to visualize difference-in-differences for both binary and continuous treatment? Do I regress the outcome variable on the set of controls but exclude the treatment variable and ...
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### How do I interpret a “difference-in-differences” model with continuous treatment?

How do I interpret the ATE coefficient (i.e., the post-treatment indicator interacted with the continuous variable)? Does it make sense? Should I break it down into subgroups and just run a fixed ...
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### Who conjectured that every correlation is caused by causal mechanisms?

I remember reading about this conjecture in Causality (Pearl, 2000). It states that every dependency between random variables can be explained (or originates from) a purely causal model. Of course ...
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### How to show influence of a treatment group?

Instrumental variables regression is often used in economics to infer causal relationships. For instance, if we are interested in the effect of remittances (X) from abroad on home consumption (Y), we ...
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### How can I compute cross-correlation and auto-correlation in R using pooled data?

I'm trying to perform a lagged linear regression on time series data sourced from ~10,000 hospital patients, for the purpose of estimating causal relationships between administration of a drug and a ...
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### Causal inference from Cross sectional study

As far I know that, causal inference can make for longitudinal study. Is their anyway way to make causal inference from cross sectional study design? If yes, how can I do this? Please share if any ...
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### Dealing with constraints in probabilistic graphical models

Suppose I have a graphical model with i.i.d. $\Lambda_i \sim exp(\lambda),\ \ i = 1,...,n$, and $\bf{\Lambda} = \sum_{i=1}^{n}\Lambda_i$. Imagine that that these $n$ lambda and this capital ...
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### How to identify the underlying mechnism in regression (to preserve the causality)?

everyone,I recently encounter a problem when doing some empirical work. Say, with a cross section dataset,I'm studying the effect from A to Y, including a branch of control variables X,of which A is a ...
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### How to do regression if one is not sure of dependent variable?

I have data on age, gender, height and weight of subjects, and also levels of 2 chemicals in blood of these subjects (chem1 and chem2). It is not clear whether chem1 affects chem2 or chem2 affects ...
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### Isolating influence of sampling from actual change

Say I want to evaluate teams' batting coaches in a hypothetical baseball league. It's an unusual league in that there is no control over (and large fluctuation within) the number of at-bats each ...
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### What are the main differences between Granger's and Pearl's causality frameworks?

Recently, I ran across several papers and online resources that mention Granger causality. Brief browsing through the corresponding Wikipedia article left me with the impression that this term refers ...
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### Should I use the t-test or the Wilcoxon rank sum test given these qqplots and Shapiro-Wilk stats [duplicate]

I have 4 groups and I want to test if the pairwise difference in means are significantly different. There are 6 pairwise differences. The QQnorm plots of the 4 groups look like this: The ...
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### Establishing causality under conditions of certainty

I'm currently reading "Causality: Models, Reasoning, and Inference" by Judea Pearl. Early on, he states that the development assumes that there are no certain entailments, no 1 or 0 probabilities -- ...
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### Names for some canonical directed causal graphs/illustrations of some canonical causal relationships?

Certain names are used for structures or node relationships that appear in acyclic, directed graphs (DAGs). Often these DAGs are interpreted causally. Here's a partial list for relationships that ...
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### What are the best empirical studies comparing causal inference with experimental, quasi-experimental, and non-experimental techniques?

The Issue: People attempt to draw causal inferences using many different statistical techniques (e.g. regression, propensity score matching, regression discontinuity, instrumental variables, etc.). ...
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### Necessary conditions for causality

E. Tufte writes: 'Probably the shortest true statement that can be made about causality and correlation is "Empirically observed covariation is a necessary but not sufficient condition for ...
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### Need a statistic for comparing “strength” of Markov blankets in a Bayesian network

Working with Bayesian networks. I take a given network structure and fit its parameters on data. I am looking for a statistic based on those parameter estimates that allows me to compare Markov ...
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### Time domain regression - determining lagged predictors

Determining lifestyle factors affecting a medical symptom I have a dataset with n=200 records corresponding to contiguous days and consisting of 1 continuous output variable (a medical symptom) and ...
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### Does rejection of null hypothesis in multiple regression entail causation?

We make a model of the following form: $$y = \beta_0 + \beta_1x_1 + \beta_2x_2 + \epsilon$$ and with $n=1,000$, $\hat\beta_1$ has a p-value <0.001. If our data and data collection meets ...
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### Can two linear regression variables be perfectly correlated but not share a single causal chain ancestor?

A causal chain lists event (or fact) $y$ with all its causal antecedents. We make a model of the following form: $$y = \beta_0 + \beta_1x_1 + \beta_2x_2 + \epsilon$$ $\hat\beta_1$ has a p-value ...
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### Measuring effects with longitudinal data

Problem: I have sales data through time e.g. how much each user spent on each shopping trip. I am interested in certain events (think users switching to Amazon Prime for instance). I know the date ...
When doing Mahalanobis matching to improve covariate balance for causual inference, how come if the treated units aren't subsampled only the control covariance matrix is used $S_c$ as opposed to the ...