抄録
Ogawa, Ikeda and Kageyama (1984) gave a necessary and sufficient condition for the connectedness of an m-associate PBIB design by using a regular representation of the association algebra. In this note, the same result is derived by a very elementary approach. The expression given here is easy to apply and is a little different from theirs. Furthermore, the connectedness of various 3-associate PBIB designs is examined along with their robustness.
