Going APE! is a National Science Foundation-funded research/development project to investigate how to develop Exploratorium exhibits that elicit active prolonged engagement (APE) among casual museum visitors. As part of this research/development process, Selinda Research Associates, Inc. (SRA) conducted a summative evaluation to assess how and to what extent the exhibit units developed by the Exploratorium team were in fact APE exhibits. This report is the second of two distinct phases of the summative evaluation study. The first phase of the summative evaluation compared visitor engagement at