Fig. 2. Histogram of the average normalized gain <g>: red bars show the fraction of 14 Traditional (T) courses (2108 students) and green bars show the fraction of 48 Interactive Engagement (IE) courses (4458 students), both within bins of width <g> = 0.04, centered on the <g> values shown. (Same as Fig. 2 of Hake 1998a.)