This resource is a formal study assessing student understanding of measurement and uncertainty.  It was administered to more than 500 students at two large research universities to address these questions:  1)  How does student understanding change over one semester from participating in an introductory physics course with a lab, and 2) What patterns exist in student reasoning pertaining to measurement and uncertainty prior to instruction?  The test was administered to students in three groups:  traditional laboratory lab sections of first semester physics, an experimental (SCALE-UP) section of first semester physics, and students in first semester physics. The results were analyzed using a mixture of qualitative and quantitative methods.  The study shows that current instructional techniques improve student understanding, but that many students exit the introductory physics lab course without coherent understanding for the concept of measurement and uncertainty, regardless of the instructional model used.