According to the article, what is the benefit of using a graph to study the results of a behavior modification plan? (Site 2)

Most data collection can be graphed (occasionally a table is more appropriate). Graphs quickly reveal progress or lack thereof. They allow for evaluation of hypotheses as to what happened (or didn't). Small variations in behavior are normal. Judge progress based on viewing multiple data collection periods (that might mean, for example, looking at a week's worth of data, graphed by days).