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Commit 1502be4b authored by Riku-Laine's avatar Riku-Laine
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1st chapter of results

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......@@ -27,7 +27,7 @@ sources_ignored
# these rules might exclude image files for figures etc.
# *.ps
# *.eps
# *.pdf
*.pdf
## Generated if empty string is given at "Please type another file name for output:"
.pdf
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paper/img/without_unobservables.png

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......@@ -124,6 +124,15 @@ which should be equal to
\begin{equation}
F(\featuresValue_0) = \int {\prob{\featuresValue} \indicator{\prob{\outcome = 0| \decision = 1, \features = \featuresValue} > \prob{\outcome = 0| \decision = 1, \features = \featuresValue_0}} d\featuresValue}
\end{equation}
\note[RL]{
Should the inequality be reversed? With some derivations
\begin{equation}
F(\featuresValue_0) = \int {\prob{\featuresValue} \indicator{\score{\featuresValue} > \score{\featuresValue_0} } ~ d\featuresValue}
\end{equation}
}
The bail-or-jail scenario is just one example of settings that involve a decision $\decision \in\{0,1\}$ that is based on individual features \features and leniency (acceptance rate) \leniency -- and where a behavior of interest \outcome is observed only for the cases where \decision = 1.
The diagram of the causal model is shown in Figure~\ref{fig:causalmodel}.
Our results are applicable to other scenarios with same causal model.
......@@ -142,6 +151,7 @@ We will use existing machine-learning techniques from the literature to learn fu
The challenge we face is to estimate accurately the performance of the decision system -- given that we are in a `selective labels' setting.
Performance is measured {\it for a given leniency level} as the rate at which bail is granted {\it and} the defendant violates it.
In other words, performance is measured as the probability that a decision lead to undesired outcome.
\section{Analysis}
We wish to calculate the probability of undesired outcome (\outcome = 0) at a fixed leniency level.
......@@ -170,17 +180,9 @@ the {\it generalized performance} \generalPerformance of that model is given by
Equation~\ref{eqn:gp} can be calculated for a given model \datadistr{\featuresValue} = \prob{\features = \featuresValue} of individual features.
Alternatively, we can have an empirical measure \empiricalPerformance of performance over the $\datasize$ data points in dataset \dataset, given by the following equation.
\begin{equation}
\empiricalPerformance = \frac{1}{\datasize} \sum_{(\featuresValue, \outcomeValue)\in\dataset} \indicator{\outcomeValue = 0} \indicator{F(\featuresValue) < r}
\label{eqn:gp}
\end{equation}
\note[MM]{
Use the following for empirical performance?
\begin{equation}
\empiricalPerformance = \frac{1}{\datasize} \sum_{(\featuresValue, \outcomeValue)\in\dataset} \score{\featuresValue} \indicator{F(\featuresValue) < r}
\label{eqn:gp}
\end{equation}
}
\subsection{Comments}
Roughly speaking, the above formulas should work well if `bail' cases (\decision = 1) cover well the area spanned by the observed features of defendants -- i.e., we do not have large areas of \features with no or too few bail cases.
......@@ -196,6 +198,33 @@ Lack of data for large areas of \features is a potential problem for the {\it co
Unlike contraction, though, our approach does not require to have data at all leniency levels.
Moreover, it is easy to see based on the derivations of Eq.\ref{eqn:gp} that our approach would work identically in the case where defendants are not assigned to judges at random (i.e., if there was a causal relation $\features\rightarrow\leniency$).
\section{Results}
Below we present our results in various settings.
\subsection{Without unobservables}
The causal model for this scenario corresponds to that depicted in Figure \ref{fig:causalmodel}.
For the analysis, we assigned 500 subjects for each of the 100 judges randomly.
Every judge's leniency rate $\leniency$ was sampled uniformly from a half-open interval $[0.1; 0.9)$.
Private features $\features$ were defined as i.i.d standard Gaussian random variables.
Next, probabilities for negative results $\outcome = 0$ were calculated as
\[
\prob{\outcome = 0| \features = \featuresValue} = \dfrac{1}{1+\exp\{-\featuresValue\}}
\]
and consequently $\outcome \sim \text{Bernoulli}(1 - \prob{\outcome = 0| \features = \featuresValue})$.
The decision variable $\decision$ was set to 0 if the value $\prob{\outcome = 0| \features = \featuresValue}$ resided in the top $(1-\leniencyValue)\cdot 100 \%$ of the subjects appointed for that judge.
Results for estimating the causal quantity $\prob{\outcome = 0 | \doop{\leniency = \leniencyValue}}$ with various levels of leniency $\leniencyValue$ are presented in Figure \ref{fig:without_unobservables}.
\begin{figure}
\begin{center}
\includegraphics[width=\columnwidth]{img/without_unobservables.png}
\end{center}
\caption{$\prob{\outcome = 0 | \doop{\leniency = \leniencyValue}}$ with varying levels of acceptance rate. Error bars denote standard error of the mean across simulations.}
\label{fig:without_unobservables}
\end{figure}
% \textbf{Acknowledgments.}
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