Theoretical comparisons of average normalized gain calculations

Since its introduction, the normalized gain or the g-factor has been widely used in assessing students' performance in pre- and post-tests. The average g-factor can be calculated using either the average scores of the class or individual student's scores. In general, these two calculations produce different results. The nature of these two results is explored for several idealized situations. The results suggest that we may be able to utilize the difference between the two results to extract information on how the population may have changed as a result of instruction. (c) 2006 American Association of Physics Teachers.