Question

Explain why “too little” variation appearing on a control chart need not be a “good” sign.

Answer 1

We know that if a data point falls outside the control limits, we can assume that the process is probably out of control and that an investigation is warranted to find and eliminate the causes. Control chart concept is mainly linked to normal distribution with specified mean and standard deviation. In this regard, variation needs to be according to a specific distribution (like normal model).

and if the variation is too little it doesn't necessarily means it is good as the variation needs to be according to a specific distribution which not always means it should be less.

thus we can say that “too little” variation appearing on a control chart need not be a “good” sign.

P.S. (please upvote if you find the answer satisfactory)