Based on the standard error of measurement, Holland (1985) suggested the "rule of eight" for determining the meaningfulness of differences between two summary scores on the Self Directed Search. The present study empirically examined the rule's validity for practice. The participants were 2397 (1497 females and 900 males) undergraduate students enrolled in the exploratory major at a large Midwestern university. The results strongly supported the interpretive rule of eight. For those participants who scored a primary-code distinction of eight or more points, the hit rate was 55% with a kappa of 0.38. This compared to a hit rate of 40% with a kappa of 0.21 for those participants with less than eight-point distinction between their top two scores. The authors also discuss the practical implications for interpreting SDS results using the "rule of eight." (Contains 1 table and 1 figure.)