Five practices that are fundamental to scientific inquiry are represented in TIMSS 2019:
1. Asking questions based on observations—Scientific inquiry includes observations of phenomena in the natural world. These observations, when considered together with theory, lead to questions, which are used to formulate testable hypotheses to help answer those questions.
2. Generating evidence—Testing hypotheses requires designing and executing systematic investigations and controlled experiments in order to generate evidence to support or refute the hypothesis. Scientists relate their theories to properties that can be observed or measured in order to determine the evidence to be gathered, the equipment and procedures needed to collect the evidence, and the measurements to be recorded.