A lower bound on the average size of a connected vertex set of a graph

The topic is the average order of a connected induced subgraph of a graph. This generalizes, to graphs in general, the average order of a subtree of a tree. In 1984, Jamison proved that the average order, over all trees of order n, is minimized by the path Pn. In 2018, Kroeker, Mol, and Oellermann conjectured that Pn minimizes the average order over all connected graphs. The main result of this paper confirms this conjecture.