T
Dear all,
Can someone please help me in the following three issues,
1- What information is provided by the operating characteristic curve of a control chart?
2- Is the average run length performance of a control chart a more meaningful measure of performance than the type I and type II error probabilities? What information does ARL convey that the statisitical error probabilities do not?
Also, what do we mean by "false alarm" in relation to ARL. I thought a point outside 3 sigma control limit will require investigation - it could be false or true! What is the benefit of saying in advance that through ARL (if there is no shift in process mean) on an average it would take 370 samples before it gives a "false alarm". Can there be no point outside the limit before 370 point plot?
3- Why lower control limit for R chart is usually "0"?
I am going through so many books, but could not find an answer that I can understand. I need to have conceptual understanding for the above three.
Thanking you all in advance.
your friend,
taha.
Can someone please help me in the following three issues,
1- What information is provided by the operating characteristic curve of a control chart?
2- Is the average run length performance of a control chart a more meaningful measure of performance than the type I and type II error probabilities? What information does ARL convey that the statisitical error probabilities do not?
Also, what do we mean by "false alarm" in relation to ARL. I thought a point outside 3 sigma control limit will require investigation - it could be false or true! What is the benefit of saying in advance that through ARL (if there is no shift in process mean) on an average it would take 370 samples before it gives a "false alarm". Can there be no point outside the limit before 370 point plot?
3- Why lower control limit for R chart is usually "0"?
I am going through so many books, but could not find an answer that I can understand. I need to have conceptual understanding for the above three.
Thanking you all in advance.
your friend,
taha.
Last edited by a moderator: