Scientific knowledge refers to facts, concepts, principles, laws, theories, and models…. Understanding science requires that an individual integrate a complex structure of many types of knowledge, including the ideas of science, relationships between ideas, reasons for these relationships, ways to use the ideas to explain and predict other natural phenomena, and ways to apply them to many events. Understanding encompasses the ability to use knowledge, and it entails the ability to distinguish between what is and what is not a scientific idea (NRC, 1996, p. 23).
Although understanding has a higher status in science education than knowledge, it is a mistake to think that all instruction or assessments should aim for the higher level of outcome. Indeed, when students fail at complex tasks, one never knows whether they are lacking specific skills or the knowledge needed for success unless one also has examined these requisites. For example, at the beginning of their units on the phases of the moon and static forces, Mr. Gilbert and Mr. Hull probed their students’ knowledge of the phenomena being investigated to establish a foundation on which to build more complex ideas.
Some of the abilities of inquiry can be assessed in a relatively straightforward way. For example, teachers can observe and listen to students to determine whether they can “use data to construct a reasonable explanation” (as specified in the K-4 standard), “develop descriptions, explanations, and models using evidence” (5-8), and “formulate and revise scientific explanations and models using logic and evidence” (9-12).
Other inquiry abilities, such as designing and conducting a scientific investigation, are more complex assessment challenges. Champagne, Kouba, and Hurley (in press) have proposed that teachers assess student inquiry by examining four phases of student investigations: precursor, planning, implementation, and closure/extension. For each phase, the teacher should delineate the expected products, abilities, and information. For example, in the planning phase the products include the plan, its rationale, and critiques of peers’ plans; abilities include developing a plan, explaining it, and revising it; and the information includes descriptions of characteristics of investigations whose methods are well matched to the question under investigation.
DeJong and Van Joolingen (1998) have summarized a parallel body of research done on inquiry abilities and understandings. Students often are unfamiliar with what a hypothesis should look like (i.e., variables and the relationships between them), are not able to state or adapt hypotheses on the basis of data gathered, and avoid hypotheses that have a high chance of