8. Use the motivation in Chapter 17 to assess an experimental set up for a firm manager, meant to estimate the uncertainty regarding a skills training program. A manager wants to know the effects on worker productivity of an online skills training, but knows the training is costly and takes time -- thus could be a failure if implemented. It assigns one of its plants to be a control group (and not receive the training) and one to be a treatment group (and receive the training). The pre-training and post-training productivity levies are given in the table below.

Group (plant)	pre-training (bold is observed)	post-training (bold is observed)
Control (plant 1)	30	70
Treatment (plant 2)	20	90

What assumption(s) do we have to make to make the experiment yield actionable results?

Draw a simple figure showing the potential trends in the 2 groups before and after the training.

What is the difference in difference estimate (DiD), in terms of productivity score? Show the calculation.

Does the training program seem like a good investment?