... causation isnot a reason to abandon correlation, but rather to under-stand the limits of this tool, to use it to test hypotheses,and to accumulate information over time to guide andinform effective ... helps to test prevailing hypotheses about student achievement. In the case of writing (with, ofcourse, editing, revision, and rewriting), the existence ofthe correlation to higher student achievement ... some instances of low achievement, ifthe cause variables are highly related to achievement then at leastyou have a blueprint for action and a deep understanding of how to improve performance...