Any changes that you implement naturally have an impact. Sometimes these changes are necessary in order to provide customers with the value they want. Other times they are needed to control waste and defects in production or to achieve Heijunka (leveled workloads). In any case, when we work with Lean the impact should focus on no waste, no defects in production, and no wasted time.
It is usually wise to test the changes before a full-scale implementation to see if the desired results are going to be achieved. Sometimes we can execute that experiment very reasonably with a small test sample, a focus group, or even a simple training exercise. In other instances, we need to test new machinery and processes on a larger scale to see what happens.