Part of Yale's Overcoming Dyslexia course, this lesson tackles a practical question for teachers and parents: how do you tell whether a reading intervention is actually working? The instructor walks through the kinds of evidence that count, distinguishing anecdotal impressions from measurable outcomes like standardized reading assessments and controlled comparisons between programs. The discussion sets up criteria for evaluating claims made by commercial reading curricula and tutoring programs, a topic directly relevant to families and educators trying to choose among competing options for a struggling reader. As the first half of a two-part lesson, it lays groundwork on research design and testing before presumably turning to specific evaluation methods in the second part. The tone is practical rather than theoretical, aimed at giving non-specialists tools to judge effectiveness claims rather than surveying dyslexia research broadly.