(2) ability to use a simple system model to find predictable factors. (3) ability to float or revise a model to show the relationship between variables, including models that cannot be observed but can predict apparent phenomena, and (4) development of a model (based on evidence) to compare what happens if a system variable or component changes. This skill assessment is conducted on the experimental and control class. In skill assessment, there are several criteria derived from the indicators contained in Table 2