© 1986 by Biometrika Trust
Triangles and efficiency factors
Department of Actuarial Mathematics and Statistics, Heriot- Watt University Edinburgh EH14 4AS, U.K.
Department of Mathematics, Royal Holloway College, University of London Egham, Surrey, TW2O 0EX, U.K.
We show that the number of triangles in the variety-concurrence graph of a regular-graph design can be used to derive upper bounds on the hatmonic-mean efficiency factor. The best alpha-lattice designs and the best cyclic designs have efficiency factors very close to the bounds. Our investigation gives insight into the structure of such designs. We see also that a certain type of regular-graph group-divisible design has a minimal number of triangles.
Key Words: Alpha-lattice design Cyclic design Incomplete block design Upper bound on efficiency factor Variety-concurrence graph