<em>Random variation in a process indicates </em><em><u>stability</u></em><em>; whereas non-random variation indicates process </em><em><u>instability</u></em><em>.</em>
When there is random variation in a process, it means that the process is stable and under control such that the only variations are those expected to be in the process.
When the variation is non-random however, it points to instability in process because this variation is special and not inherent in the process.
