  The average order of the connected induced subgraphs of a graph $G$ is called
the mean connected induced subgraph (CIS) order of $G$. This is an extension of
the mean subtree order of a tree, first studied by Jamison. In this article, we
demonstrate that among all connected block graphs of order $n$, the path $P_n$
has minimum mean CIS order. This extends a result of Jamison from trees to
connected block graphs, and supports the conjecture of Kroeker, Mol, and
Oellermann that $P_n$ has minimum mean CIS order among all connected graphs of
order $n$.
