In the context of Problem 2.13 , suppose $y_{i}$ is also binary. For concreteness, $y_{i}$ indicates whether worker $i$ is employed after a job training program, where $y_{i}=1$ means has a job, $y_{i}=0$ means does not have a job. Here, $x_{i}$ indicates participation in the job training program. Argue that $\widehat{\beta}_{1}$ is the difference in employment rates between those who participated in the program and those who did
not.