Question

Choose the best answer. A process is out of control if:

one point outside the control limits is found.

one point outside the control limits is found or there are nine consecutive points above or below the mean.

there are nine consecutive points above or below the mean.

Answer 1

we know that the two main conditions for the process A to be out of control are

(A) it must have at least one point that is outside the 3 sigma level

(B) it must have either 9 consecutive points on the upper side of mean or 9 consecutive points on the lower side of the mean

So, option 1 and 3 are incorrect or we can say incomplete because both these options have only half of condition

option 2 is correct answer because it has both the necessary condition that we mentioned above.

therefore, answer is option 2