Questions tagged [omitted-variable-bias]

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Distinguishing between effects of two variables on y

Assume that we have the linear regression model: $$ y=\beta+\beta_{1}x+\epsilon $$ We estimate the model by OLS, and we get $\hat{\beta}_{1},$ However, there is another variable $z,$ which is both ...
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Does omitted variable bias affects coefficients for those variables that are not correlated with the error term? (When their is one variable that is)

Does omitted variable bias affects coefficients for those variables that are not correlated with the error term? (When there is one variable that is.) I found two answers, but they appear to be ...
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Can you use GMM to overcome time-variant omitted variable bias resulting from FE?

I am looking at a FE model on the effects of R&D expenditure on labour productivity but not sure how to address the possible endogeneity resulting from time varying omitted variable bias. I cannot ...
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My instrument (z) only affects y through x, but y affects z directly. Is my instrument valid?

I'm running a regression model to test whether unionisation rates have an impact on wages. I've introduced an instrumental variable: public support for unions. As far as I can tell, this instrument ...
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Selecting Fixed effects when individual and group data is available

I'd like to know the framework on how to decide what fixed effect(s) to set when one has individual observations e.g., firms and these observations can be grouped e.g., industries. I understand that ...
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Question about statement in Oster (2019): variation in a control

In Oster (2019), she discusses how authors typically include controls and examine coefficient stability as a way to test for presence of confounding, and points out that researchers should consider ...
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Do insignificant variables result in a specification error?

I am trying to understand omitted variable bais better. I know that it detects irrelevant variables, but are irrelevant variables and insignificant variables synonymous here? If I have a regression ...
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2 answers
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Using a DAG to understand omitted variable bias in OLS vs Binary Dependent Variable Regression

Suppose I have three variables. $A$ and $U$ are continuous variables but $U$ is unobserved. $Y$ is the binary outcome. $A$ and $U$ are independent. Let the true model be from the typical probit or ...
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Instrument validity: does a positive and significant coefficient on Z in a regression of Y on X and Z pose a problem?

I have an initial regression of Y on X and Z. Both of my coefficients on X and Z are non-zero and strongly statistically significant. X and Z are correlated but I am told collinearity shouldn't be an ...
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Should I adjust for a confounder when it is colinear with a predictor?

Suppose the DAG in the population is as follows: We observe both $X_1$ and $X_2$. We are interested in the effect of $X_1$ on $Y$. We want to use OLS to estimate the relationship. Now if I take $X_2$ ...
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Trade-off between omitting variables or dropping observations in multivariate logistic regression

Say you are selecting $n$ observations from a complex survey of $N$ individuals to create an analytical sample of relevant observations; and that you intend to fit a binomial multivariate logistic ...
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VAR model variable selection

I'm required to use two time series models in my exam project. I want to use a stock price of an energy company, and then explain it first using ARIMA, and then adding other variables and using VAR. ...
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Is omitted variable bias possible with a perfectly correlated dependent and independent variable?

Suppose $X$ and $Y$ are perfectly correlated, and we fit a model $Y=a+bX+\epsilon$. Is it possible that there would be omitted variable bias in this situation? Intuitively, I think so, but I'm ...
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How to test whether OVB by examining two regressors (X_1, X_2) using hypothesis test with null hypothesis H0: corr(X_1,X_2) = 0

Suppose you have an i.i.d. sample {(π‘Œ , 𝑋 , 𝑋 ): 𝑖 = 1, ... , 𝑛}. You want to estimate the causal effect of 𝑋1 on π‘Œ. You first run a regression π‘Œ = 𝛼0 + 𝛼1𝑋i + 𝑒i and get the following ...
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Difference Omitted Variable Bias and Confounding?

Is there a difference between omitted variable bias and confounding bias in linear models? To my knowledge, when investigating the causal effect of $X$ on $Y$, a confounder is a variable $Z$ that is ...
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Endogeneity coming from omitted variable vs measurement error

Can someone explain more clearly what is a measurement error and how is it different from omitted variable. I know the theoretical implications, but I don't really know how to tell which problem I'm ...
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Omitted Variable Bias (OVB) and multicollinearity

In a linear regression model, the reason we control for variables is to prevent the omitted variable bias (OVB). That is, suppose we are trying to fit the model $$ Y = \beta_{0} + \beta_{1}X_{1} + \...
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Question about regression and deriving omitted variables

usually when I see derivations of ommited variable bias, I see something of the sort: from y=xb + $\eta$, and looking at the for formula for the slope estimate: $cov(x,y)$$/var(x)$ $cov(x,xb+\eta )$$/...
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Using an IV when there is more than one omitted variable

I am trying to estimate the following model: $$y=B_0 + B_1x_1 + B_2x_2 + B_3x_3 + e$$ However, I have an omitted variable bias because $x_2$ and $x_3$ are not observed. Situation 1 If I have an (...
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25 votes
3 answers
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Can a confounding factor hide a possible causal relationship? (as opposed to find a spurious one)

I'm a rookie with statistics, and I'm struggling to understand this: it is well known that a confounding factor can cause a spurious association, leading to rejecting a true null hypothesis (i.e. due ...
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2 votes
1 answer
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Does confounding always imply endogeneity?

I'm a bit confused with the definitions regarding causal inference. My question is whether we can call measured confounding an endogeneity problem?
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Are coefficients that are zero omitted variable bias?

If a regression coefficient is essentially zero, doesn't that imply that there is (massive) omitted variable bias? That is, the change must then exist in the error term. The classic definition of OVB ...
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8 votes
2 answers
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Omitted variable bias vs. Multicollinearity

There's seems to be a bit like catch 22: suppose I am doing linear regression, and I have 2 variables that are highly correlated. If I use both in my model, I will suffer from multicollinearity, but ...
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2 votes
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109 views

Can an omitted random variable cause "omitted variable bias"?

Suppose we have a linear regression: Y = mx + b where X is the independent variable of interest, in this case "scoops of ice cream per order" at an ice cream shop, b is the error term, and Y is the ...
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