Questions tagged [selection-bias]

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2answers
43 views

Favored methods for overcoming selection bias (special attention to healthcare fields)?

I am frequently measuring the effect of behavioral health treatment interventions on outcomes of interest. However, comparing the relative efficacy of different types of treatment is tricky - more ...
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0answers
21 views

How to correct for selection bias in a situation where usual Heckman correction won't do? Should I even do it?

I have a question about how to correct for selection bias in an experience. In this experience, we evaluate the impact of slight tweaks in phrasing on web surveys participation. For example, if you ...
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1answer
37 views

What is the correct notation for expressing a mixture of distributions?

In a normal classification context, the training instances are drawn from a distribution $D$ which is defined over $X \times Y$, where $X$ is the feature space and $Y$ is the label space. When ...
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1answer
36 views

Sample selection bias

In Learning and Evaluating Classifiers under Sample Selection Bias, we suppose that examples $(x, y, s)$ are drawn independently from a distribution $D$ with domain $X × Y × S$ where $X$ is the ...
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0answers
45 views

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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0answers
16 views

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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0answers
101 views

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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0answers
24 views

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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0answers
28 views

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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0answers
56 views

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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0answers
19 views

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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0answers
113 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
69 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 ...
0
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1answer
110 views

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 ...
2
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1answer
198 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 ...
4
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2answers
171 views

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 ...
3
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2answers
174 views

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 ...
2
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1answer
125 views

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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0answers
58 views

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 ...
4
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0answers
203 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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0answers
50 views

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 ...
1
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2answers
836 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 ...
9
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1answer
13k views

Interpretation of coefficient of inverse Mills ratio

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