Science assessments should evaluate the full complement of inquiry practices (NGSS, 2013). Our previous work has shown that a large proportion of students' open responses did not match their scientific investigations (Li et al., 2017a). The present study both unpacks and compares the sub-components underlying students' performance for experimenting to their written open responses. These findings have implications for the assessment of inquiry practices, design of real-time scaffolding, and teachers' instruction of science. [This paper was published in: "Rethinking Learning in the Digital Age: Making the Learning Sciences Count. 13th International Conference of the Learning Sciences," 2018.]