## Query on Control Chart PMP question

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psganesh.84
Posts: 7
Joined: Fri May 16, 2014 2:47 pm

### Query on Control Chart PMP question

A production process has been defined as part of an industrial equipment manufacturing project. The process is intended to produce steel bolts with a length of 20 cm. The control limits are 19.955cm and 20.045cm.
The measurements made at the end of the process yielded the following results:

20.033cm, 19.982cm, 19,995cm, 20.006cm, 19.970cm, 19.968cm, 19.963cm, 19.958cm, 19.962cm, 19.979cm, 19.959cm.

What should be done?

a)The process is under control. It should not be adjusted.
b)A special cause should be investigated, the process should be adjusted.
c) The control limits should be adjusted.
d) The measuring equipment should be recalibrated.
harin4627
Participant
Posts: 92
Joined: Thu May 29, 2014 6:50 pm

### Re: Query on Control Chart PMP question

First check: all the measurements are within control limits. Hence no problem.
Second check: find the mean value. (20.045-19.955)/2=.09/2=.045 that is the mean value is 20.00 (equal distance to upper and lower control limits)
Now again check the values: last seven points are below the mean value 20, rule of seven applies. So the answer should be “A special cause should be investigated, the process should be adjusted”
Am I on the right direction?
psganesh.84
Posts: 7
Joined: Fri May 16, 2014 2:47 pm

### Re: Query on Control Chart PMP question

Thank you very much Hari , very good explanation !
indusharma
Super Member
Posts: 349
Joined: Wed Dec 11, 2013 2:55 am

### Re: Query on Control Chart PMP question

Well explained
Indu Sharma
PMP Trainer
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