A pilot program implementing a new screening tool for drug and alcohol abuse has proven to be very effective by the staff of an acute medical unit. As the staff prepares to utilize this tool on a regular basis, which factor has proven most effective in this decision?

internal evidence

Explanation:

Based on the information provided within the question it can be said that the factor that has proven most effective in this decision was internal evidence. This factor refers to information that has been gathered from the internal sources in which the contents have been discussed. Which in this scenario were the staff of an acute medical unit within the pilot program.