Questions tagged [selection-bias]

Bias introduced by non-random selection of observations, such that the sample is not representative of the underlying population.

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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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Which DAG would explain the lack of correlation between height and performance in NBA players?

A classic example of "selection bias" involves looking at the performance of professional basketball players. The example goes, among NBA players there is no correlation between height and ...
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1answer
181 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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76 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 ...
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24 views

Logistic regression for case-control studies

If I have designed a study where participants from 3 disease groups of fixed size were being sampled and suppose the three groups A, B and C are of sizes n_A=50, n_B=50 and n_C=100. Group A is a ...
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35 views

Intended selection bias

Sampling or selection bias is often presented as something that has to be overcome, avoided, or at least appropriately considered because it's a problem otherwise. I wonder how often situations arise (...
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18 views

How to estimate the impact of policy on labor supply if the policy causes death, too?

Suppose people can make only one of three choices A, B, C. A = Death B = Survive, Work C = Survive, Not work I want to study the impact of an exogenous policy on ...
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59 views

Is this referring to the true underlying distribution, or the distribution of our sample?

I am currently studying the paper Learning and Evaluating Classifiers under Sample Selection Bias by Bianca Zadrozny. In the introduction, the author says the following: One of the most common ...
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60 views

Selection bias in categorical independent variable in regression analysis

I have an issue with selection bias in my independent variable and I am uncertain of the best approach to correct for it. I'm looking at soccer data and trying to make some forecasts on players from ...
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Correcting for known imputation bias

I have a survey sample which includes income values by type of income for a significant number of high-income households. Some of the income data is measured, i.e. present in the responses of the ...
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117 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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75 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 ...
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2answers
45 views

Regression with endogenous dummy variables

Suppose I have 1,000 observations on variable Y, and I regress Y on just a dummy variable (d), in two different regressions. In the first regression, I set d equal to 0 for the first 500 observations, ...
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19 views

Using a sample of paid survey respondents to bias correct lower response rate among larger non-paid sample

I'm running a tracker survey on a website that has a low response rate of about 2%. The survey is not incentivized but the website traffic is large enough in volume I can always meet my sample target ...
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15 views

Adjusting for selection bias

I need to estimate the total financial impact of fraudulent cases in our business sphere. I have a dataset of audited cases where the selection process is guided by risk assessment and another very ...
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15 views

Dealing with Heckman correction and sampling bias in an experiment without instruments

Imagine a randomised experiment where workers are offered a job for \$x, and they can choose to reject the offer, accept $x or propose some counteroffer x' > x. An equal number of workers are ...
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9 views

Testing a sequence of random variables for hypothesis that distribution changes at single discrete point

Suppose we have an ordered sequence of independent random variables, $X_1, \ldots X_m, X_{m+1}, \ldots, X_n$, where under the null hypothesis, $X_{1..n}$ are identically distributed with $$\mathbb{E}[...
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15 views

Lagged dependent variables: Is it safe to ignore bias over a long time horizon?

Suppose I have a Poisson model which investigates the effect of a county level policy on robbery counts. Here is the basic specification: $$ \text{log}(y_{it}) = \theta y_{i,t-1} + \sum_i\text{County}...
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9 views

Interaction term and selection

I am estimating a probit model, say : $Pr(y = 1 \mid x_1, sex_.woman) = \Phi(\alpha + \beta_1 x_1 + \beta_2 sex.woman + \beta_3 x_1sex.woman)$ The independent variable of interest is $x_1$. I find ...
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Hidden Traits in Selection

Is there a name for an artefact of selection where you think you are selecting for a number of traits and you find, that in the set that is output, there is a hidden shared trait between everything in ...
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9 views

Bayesian Variable Selection Bias

Suppose that we have a design matrix $X$, $n\times p$, a vector $Y$, $n\times 1$ and our goal is to select between the following two linear regressions $$Y_{i}=a+b_{1}X_{1}+\epsilon_{i}$$ $$Y_{i}=a+b_{...
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1answer
58 views

Endogenous Sample Selection and Heckit Correction in relation to Research Question

I am researching the funding amounts of start-ups. I am calculating two models: ...
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11 views

Truncation based on two variables

I have some data, which has been constructed from multiple API pulls. Observations have an expiry date, $x_i$, which means that observations which expire before the API pull is done do not appear in ...
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1answer
120 views

Heckman Selection (Selection vs. Outcome equation)

A common example of the Heckman selection model involves wages, which are only observed if an individual chooses to participate in the labor force. The first stage probit model dependent variable is a ...
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1answer
72 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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221 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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22 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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1answer
570 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 ...