Sankhya B (November 2011) 73:211–217 DOI 10.1007/s13571-011-0018-8 A new look at search designs K. Chatterjee · C. Koukouvinos Received: 30 August 2010 / Revised: 18 November 2010 / Accepted: 7 January 2011 / Published online: 1 October 2011 © Indian Statistical Institute 2011 Abstract Search designs were first introduced by Srivastava (1975) in order to address the problem of identifying a set of possibly non-negligible interactions. In this paper search designs for 2-level symmetric factorials are considered under the effect hierarchy principle and under a special structure. We provide designs for searching at most three two-factor interactions. Using Hadamard matrices, constructions of such designs are presented. Keywords Two level factorials · Search designs · Tree structure AMS 2000 Subject Classifications Primary 62K15; Secondary 05B20 1 Introduction Considering the hierarchy of factorial effects Srivastava and Hveberg (1992) observed a tree structure in the factorial effects when analyzing data that arises from behavioral sciences. It is logical that the non-negligibility of interactions F 1 F 2 and F 1 F 3 implies the non-negligibility of F 2 F 3 for a factorial experiment involving factors F 1 , F 2 , and F 3 . Chatterjee and Fang (2001) constructed K. Chatterjee Department of Statistics, Visva-Bharati University, Santiniketan, West Bengal, India C. Koukouvinos (B ) Department of Mathematics, National Technical University of Athens, Zografou 15773, Athens, Greece e-mail: ckoukouv@math.ntua.gr