The explanatory variable in the study is stretching before running, and the generalizability of the results to the entire school might be limited.
a) Explanatory variable: The explanatory variable in this study is stretching before running. It is the variable that is being manipulated by the PE teacher to see its effect on the mile time.
b) Generalizability: The results from the study may not be able to be generalized to the entire school as the study only involves a specific group of students who were selected randomly. To generalize the results to the entire school, a more representative sample of students would need to be involved in the study.
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