Before implementing wide$-$spread change, it's important to test your theory and the proposed solution by runnin a small$-$scale test and assessing the results on a Control Char. Which criteria have to be fulfilled to indicate that the tested solution has a positive impact? Select THREE answers.

A$.$ Only Rule A assignable cause variation is present

B$.$ A signal of assignable cause variation is present and in line with the change in physical process

C$.$ Assignable cause variation is sustained throughout the lifespan of the test

D$.$ The change represents an improvement and is desirable

E$.$ Only common cause variation is present