2. In 2018, one of the largest energy firms in the United States noted that its solar panel business was growing extremely rapidly. This growth had occurred even though the firm never had an active training program in solar panel sales for its sales force. The top management of the company believed that by instituting a comprehensive training program, its sales performance could be further improved. With this goal in mind, the firm's training department put together a comprehensive training program. Fifty sales people who had done the greatest volume of solar panel sales in the first six months of 2018 were selected to participate in the course. In the first six months of 2019, the average solar panel sales of these sales people who were trained in the course rose by 15% over the comparable period in 2018. The average sales volume of the sales people who had not participated in the training program was 20% higher in the first six months of 2019 as compared to the first six months of 2018. Based on these results the management concluded that the training program was not useful. What kind of experimental design is being used? Describe relevant potential extraneous variables in this experiment. Can this experiment design rule out these extraneous variables?