29 October 2015
I propose a method to correct for test scores manipulation and apply it to a natural experiment in the Italian education system consisting in the random assignment of external monitors to classrooms. The empirical strategy is based on a likelihood approach, using nonlinear panel data methods to obtain clean estimates of cheating controlling for unobserved heterogeneity. The likelihood of each classroomâ€™s scores is later used to correct them for cheating. The results show frequent manipulation, which is not associated with an increase in the correlation of the answers after we control for mean test scores. The manipulation is concentrated in the South and Islands, and it tends to favor female students, and immigrants in Italian tests. Finally, the negative correlation between the amount of manipulation and the number of missing answers in the difference between open ended and multiple choice questions suggest that teachers are more responsible for the manipulation than students. A simulation shows how the manipulation reduces the accuracy of an exam in reflecting studentsâ€™ knowledge, and the correction proposed in this paper makes up for about a half of this loss.
Pereda Fernández, Santiago