\( \definecolor{colordef}{RGB}{249,49,84} \definecolor{colorprop}{RGB}{18,102,241} \)
In a study of a new training program’s impact, each employee’s performance is assessed before and after, with improvement classified as 'Improved' or 'Not Improved'. Define the random variable \(Z_i\), where \(i\) is the \(i\)-th employee, to model this study.
Choose the one correct answer: