Measurement estimation: Learning to map the route from number to quantity and back

Measurement estimation has been identified as a critical area for mathematical development, yet little is known about how estimators make their judgments and how competency in measurement estimation can be supported through instruction. We present a framework in which skilled estimators move fluently back and forth between written or verbal linear measurements and representations of their corresponding magnitudes on a mental number line. With reference to the proposed framework, a review of instructional efforts to teach measurement estimation suggests they are incomplete and are limited to producing associations between isolated measurements and their referents. Recommendations are discussed for instruction that would extend students' understanding beyond these discrete points to conceptualize measurement scales and systems.