The Power Challenge is LightSail’s short placement test of approximately 40 clozes designed to identify a student’s baseline Lexile score. Each student answers clozes at the end of passages starting at his grade level. The test automatically adapts with easier or harder questions depending on the number correctly answered. A student must take the Power Challenge before checking out his first book in order for LightSail to effectively assign Power Texts at their reading level.
Please find more research behind the Lexile Framework by visiting MetaMetrics's site here: https://lexile.com/research-and-publications/research-on-products/.