Out of the 157 individuals working in the department at the beginning of our observation period (week 50/2008), 86 were selected for the experiment. Conditional on being selected for participation in the field experiment, 37 out of the 86 agents were randomly selected for participation in the treatment group. The remaining 49 agents who were assigned to the control group were trained after the post-experiment period.
Agents assigned to participate in the field experiment were randomly assigned to be treated during the treatment period, or to be treated after the end of the experiment. Due to the restriction that agents should be trained with other agents from the same team, half of the teams were randomly assigned to the treatment group, whereas the other half was assigned to the control group. Each team was then randomly split up in different training groups, due to size constraints of the training centre.