Although comparison of group means is by far the most commonly used method of assessing training effectiveness, it has been suggested that investigating differences between group means may not be the only way of assessing training effectiveness. Specifically, an investigation of differences in performance variance may reveal important conclusions not revealed by an analysis of group means. The present chapter presents the results of an investigation of whether performance variance provides incremental diagnostic information over and above information provided by an investigation of group means in the context of complex skill acquisition, retention, and transfer by reanalyzing data from two previously published long-term skill-retention studies involving different performance tasks, criterion measures (i.e., skillbased performance and declarative knowledge), and training protocols. In general, the results indicate that performance variance may provide inform - ation regarding the nature of the task itself. However, as an indicator of training effectiveness, variance provides confirmatory evidence of training effectiveness but does not provide diagnostic information over and above information provided by an investigation of group means in the context of complex skill acquisition, retention, and transfer.