Final answer:
The most important players in a substance testing program are typically the internal stakeholders, such as the program director and coordinator, whose commitment is crucial for effective program implementation and evaluation.
Step-by-step explanation:
In substance testing programs, the most important role is often played by internal stakeholders such as the program director and coordinator. These individuals are key because they are directly involved in the program's operations and have the capacity to influence both program implementation and its evaluation. As illustrated in the mini-case studies, successful program evaluations require commitment and active participation from these internal stakeholders.
In contrast, when those individuals lack commitment, as shown by the program coordinator's disinterest in evaluation, it can result in insufficient data collection and assessment of the program's effectiveness. Moreover, external stakeholders, while beneficial, may not see themselves as part of the program, which can lead to a lack of engagement and further complicate the evaluation process.