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authorStratis Ioannidis <stratis@stratis-Latitude-E6320.(none)>2013-07-07 21:21:23 -0700
committerStratis Ioannidis <stratis@stratis-Latitude-E6320.(none)>2013-07-07 21:21:23 -0700
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@@ -84,13 +84,9 @@ covariance matrices $R$ can be found in Appendix~\ref{sec:ext}.
\subsection{Budget-Feasible Experimental Design: Full Information Case}\label{sec:fullinfo}
-Beyond the cardinality constraint in classical experimental design discussed above, a
- budgeted version can also be considered.
-%depart from the above classic experimental design setting by assuming that
-Each experiment is associated with a cost $c_i\in\reals_+$. Moreover, the experimenter $\E$ is limited by a budget $B\in \reals_+$.
-The cost $c_i$ can capture, \emph{e.g.}, the amount the subject $i$ deems sufficient to
-incentivize her participation in the experiment.
-In the full-information case, the experiment costs are common knowledge; as such, the optimization problem that the experimenter wishes to solve is:
+Instead of the cardinality constraint in classical experimental design discussed above, we consider a budget-constrained version.
+Each experiment is associated with a cost $c_i\in\reals_+$.
+The cost $c_i$ can capture, \emph{e.g.}, the amount the subject $i$ deems sufficient to incentivize her participation in the experiment. The experimenter $\E$ is limited by a budget $B\in \reals_+$. In the full-information case, experiment costs are common knowledge; as such, the experimenter wishes to solve:
\medskip\\\hspace*{\stretch{1}}\textsc{ExperimentalDesignProblem} (\EDP)\hspace*{\stretch{1}}
\begin{subequations}
\begin{align}
@@ -149,7 +145,7 @@ We seek mechanisms that are \emph{normalized} (unallocated experiments receive z
We relax the notion of truthfulness to \emph{$\delta$-truthfulness}, requiring that reporting one's true cost is an \emph{almost-dominant} strategy: no subject increases their utility by reporting a cost that differs more than $\delta>0$ from their true cost. Under this definition, a mechanism is truthful if $\delta=0$.
In addition, we would like the allocation $S(c)$ to be of maximal value; however, $\delta$-truthfulness, as well as the hardness of \EDP{}, preclude achieving this goal. Hence, we seek mechanisms with that yield a \emph{constant approximation ratio}, \emph{i.e.}, there exists $\alpha\geq 1$ s.t.~$OPT \leq \alpha V(S(c))$, and are \emph{computationally efficient}, in that $S$ and $p$ can be computed in polynomial time.
-We note that the $\max$ operator in the greedy algorithm \eqref{eq:max-algorithm} breaks
+We note that the greedy algorithm \eqref{eq:max-algorithm} breaks
truthfulness. Though this is not true for all submodular functions (see, \emph{e.g.}, \cite{singer-mechanisms}), it is true for the objective of \EDP{}: we show this in Appendix~\ref{sec:non-monotonicity}. This motivates our study of more complex mechanisms.
\begin{comment}