  In response to national calls to better align physics laboratory courses with
the way physicists engage in research, we have developed an epistemology and
expectations survey to assess how students perceive the nature of physics
experiments in the contexts of laboratory courses and the professional research
laboratory. The Colorado Learning Attitudes about Science Survey for
Experimental Physics (E-CLASS) evaluates students' epistemology at the
beginning and end of a semester. Students respond to paired questions about how
they personally perceive doing experiments in laboratory courses and how they
perceive an experimental physicist might respond regarding their research.
Also, at the end of the semester, the E-CLASS assesses a third dimension of
laboratory instruction, students' reflections on their course's expectations
for earning a good grade. By basing survey statements on widely embraced
learning goals and common critiques of teaching labs, the E-CLASS serves as an
assessment tool for lab courses across the undergraduate curriculum and as a
tool for physics education research. We present the development, evidence of
validation, and initial formative assessment results from a sample that
includes 45 classes at 20 institutions. We also discuss feedback from
instructors and reflect on the challenges of large-scale online administration
and distribution of results.
