  We study the causal bandit problem that entails identifying a near-optimal
intervention from a specified set $A$ of (possibly non-atomic) interventions
over a given causal graph. Here, an optimal intervention in ${A}$ is one that
maximizes the expected value for a designated reward variable in the graph, and
we use the standard notion of simple regret to quantify near optimality.
Considering Bernoulli random variables and for causal graphs on $N$ vertices
with constant in-degree, prior work has achieved a worst case guarantee of
$\widetilde{O} (N/\sqrt{T})$ for simple regret. The current work utilizes the
idea of covering interventions (which are not necessarily contained within
${A}$) and establishes a simple regret guarantee of
$\widetilde{O}(\sqrt{N/T})$. Notably, and in contrast to prior work, our simple
regret bound depends only on explicit parameters of the problem instance. We
also go beyond prior work and achieve a simple regret guarantee for causal
graphs with unobserved variables. Further, we perform experiments to show
improvements over baselines in this setting.
