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Questions tagged [selection-bias]

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How to perform inference on inverse Mills ratio in Heckit estimation?

I want to estimate log(wages). Most wage estimations suffer from sample selection bias. So I used the two step heckit procedure to correct for it. The problem is that I get an insignificant inverse ...
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How to test for sample selection bias in heckit estimation?

I'm doing a heckit two step estimation by hand where i first estimate the labor force participation, compute the inverse mills ratio by using the linear predictors of the model and add it as an ...
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How to calculate “weight” that balances the sample dataset when we are given population categories ? (find survery weights)

I am very unfamiliar with survey designing and this might be a very basic question to statisticians and surveyors, but still, I seek help finding the weight for each sample data that will address the ...
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Sample restriction in difference in difference: interpretation of the results and (potential) bias

Within a difference in difference (DD) strategy trends of an outcome of interest are compared for the treatment and the control groups before and after an intervention. The crucial assumption is that ...
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Can selection bias be solved by including control variables?

Omitted variable bias can be solved by including covariates that are omitted. However, can selection bias also be solved by including covariates?
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Difference-in-differences: selection bias due to availability of outcome data

I have run a diff-in-diff specification to evaluate the outcome of a policy on disease treatment rate, where those countries included in the policy form the intervention group and those excluded are ...
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Logistic regression when only TRUE values are observed, but a control sample exists

I'm involved with a creel survey. We have reason to believe that anglers are keeping the larger fish they catch, or at least that a relationship exists between the size of caught fish and the ...
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48 views

Predicted values in selection model with binary outcome in R

I would like to generate predicted values for a Heckmann selection model with two probit equations (the selection equation as well as the outcome equation have binary dependent variables). According ...
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1answer
54 views

Correcting sample selection bias of binary classifiers

In fraud investigation the number of detected fraud cases can be very small when compared to the total number of cases. This would also apply to rare desease detected in a very small number of people ...
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IV-estimation vs. Heckman's selection model

I am trying to grasp the difference between IV-estimation and Heckman's selection model. I do that by considering the following set-up. My outcome if interest is y ...
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1answer
107 views

Why does weighted bootstrap have awful coverage even in toy example?

I'm interested in using the weighted bootstrap to correct for selection bias with a known form. I simulated a very simple example where the underlying data, $X$, are $N(0,1)$ and we are calculating a ...
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Is this actually an example of selection bias?

In Lesson 3, Chapter 3 of Miguel Hernán's edX course on causal diagrams, he presents this DAG: It represents a study on the effect of hormone therapy on lung cancer (whether hormone therapy causes ...
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Usage of Heckman estimation for a random sample

My colleague argues to use a Heckman Model in the following case (Agricultural economics): I have a random sample of farmers (n) of the general population N. In n some observations apply a given ...
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In what instances do we need to worry about Heckman correction for selection bias?

I understand that Heckman selection models attempt to address selection bias by running two-part models. In the oft cited example of determinants of wage offers: 1) we have a group of people who work ...
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Can the structural and the selection equation be the same in a Heckman selection model?

Consider this trivial example: a company can adopt two marketing strategies, namely aggressive ($j=0$) or defensive ($j=1$). Profits depend on which one is chosen. Thus, the "structural equation" is: ...
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40 views

Testing multiple forms of sample selection simultaneously

Consider a sample from a longitudinal survey of the labour market. Say I want to study the effect of unions on wages. There are at least three potential sources of selection I could be worried about. ...
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How to handle bias due to self-selection in one group

I want to compare two or three social groups across a set of dependent variables, using data from a longitudinal survey. The problem is that membership in one of the groups leads to a self-selection ...
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185 views

Correcting Sample Selection Bias given actual Distribution

I have two datasets, both from the same population: The samples from the first survey are quite representative of the underlying truth. However, the second survey comes with a change in distribution ...
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23 views

How does Rassumsen always get Pro-GOP Results?

(HONEST question, I am not being snarky) Not why, that is obvious…but how?? Even FOX polls skew more non-right wing! Their methodolgy seems otherwise quite fit, and it is a national poll (i.e. not ...
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Adjusting for selection bias in a structural topic model

I want to build a structural topic model that adjusts for selection bias into the sample of entities about whom documents are written. I wanted to use the stm R ...
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2answers
754 views

Different forms of Inverse Mills Ratio & their interpretation

I have noticed different authors using different forms of IMR, i.e., $\frac{f(x)}{F(-x)}$ or $\frac{f}{(1-F(x))}$ depending on whether they are modeling selection or non-selection in the first-stage ...
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Interpretation of coefficient of inverse Mills ratio

How do you interpret the coefficient of inverse Mills ratio (lambda) in two step Heckman model?