Session V (May 16, 8:30am-10:00am): Orthogonal arrays and related designs, organized by Boxin Tang 

• Title: Choosing Strength-Two Orthogonal Arrays that are Less Susceptible to Bias 

• Speaker: Bobby Mee, University of Tennessee

• Abstract: We present two examples where prior information indicates that some isomorphic fractions are better than others. There are many applications where two isomorphic orthogonal arrays will have different susceptibilities to bias.  Two-level orthogonal arrays of strength 2 that contain the all-low treatment combination or the all-high treatment combination can be shown to be more susceptible to bias for particular choices of factors or factor levels. Yet these fractions are generally the default fractions offered by design software.  By reversing the levels of a subset of factors in the orthogonal array, we expect to obtain isomorphic fractions that produce main effect estimates with less bias and which lead the researcher to better and more accurate predictions.