Andrew Heckler The Ohio State University Testing student learning: is the normalized gain valid? The "normalized gain" is a widely used quantitative measure of student learning in physics education research. While this measure has proven to be quite useful in general terms, there are several fundamental questions as to its specific meaning and validity as a uniform measure of learning. We examine the pre and post scores from several different kinds of conceptual physics tests and show that, when several statistical effects are taken into account, the normalized gain does not accurately or adequately represent the empirical data. Instead, another more simple measure is found to more accurately represent the underlying behavior of pre and post test scores. These results indicate that the normalized gain can be biased towards groups of students with high pre test scores. The results also have important implications for theories of learning and challenge commonly held assumptions about knowledge, learning, and testing.