Control Chart Question

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thiru26@gmail.com
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Control Chart Question

Postby thiru26@gmail.com Sat Oct 03, 2015 12:58 am

Q : On a control chart, if six consecutive plot points are above the mean, then what can be established about the process?
A) The process is out of control
B) The process will be out of control after plotting the seventh point.
C) The process is in control
D) Nothing can be established

What is the correct answer.
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Re: Control Chart Question

Postby ujjal_show Sat Oct 03, 2015 8:34 am

D) Nothing can be established.

because other relevant information like specification limit, control limit is missing.
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Re: Control Chart Question

Postby thiru26@gmail.com Sat Oct 03, 2015 1:55 pm

ujjal_show wrote:D) Nothing can be established.

because other relevant information like specification limit, control limit is missing.

Thanks.
Why cant C, six consecutive plot points are above the mean, which tells there is nothing wrong in the process.
How to derive for the option D, i have confused between C and D.
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Re: Control Chart Question

Postby vivek3377 Sat Oct 03, 2015 2:00 pm

And why cant it be B? Rule of 7 says, process is out of control if you have 7 consecutive points on one side of the mean (either above or below). You already have six such points. So plotting 7th point will mean the process is out of question.
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Re: Control Chart Question

Postby ujjal_show Sat Oct 03, 2015 4:01 pm

C) The process is in control, it is not true because we don,t know whether they are within the specification/ control limit too.

B) The process will be out of control after plotting the seventh point, it is not true because we don,t know if the 7th data point plot below the mean.
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Re: Control Chart Question

Postby saket Sat Oct 03, 2015 5:46 pm

Some questions may not necessary have correct answers ..... please see the old thread... :)
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Re: Control Chart Question

Postby thiru26@gmail.com Sat Oct 03, 2015 7:26 pm

manishpn wrote:http://forum.izenbridge.com/viewtopic.php?f=11&t=2208&p=8205&hilit=six+consecutive+plot+points+are+above+the+mean#p8205

Thanks for the link, but I am not authorized to view the forum.
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Re: Control Chart Question

Postby thiru26@gmail.com Sat Oct 03, 2015 7:30 pm

ujjal_show wrote:C) The process is in control, it is not true because we don,t know whether they are within the specification/ control limit too.

B) The process will be out of control after plotting the seventh point, it is not true because we don,t know if the 7th data point plot below the mean.


Question is very short, but very tricky.

I have seen same question in another forum, choose wrong answer, also again did the same mistake, couldnt understood which way the question was presented.

Your explanation helps, if I get the same question in the exam, will crack it for sure. :lol:

Thank you guys, great forum, very talented people around....
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Re: Control Chart Question

Postby thiru26@gmail.com Sat Oct 03, 2015 7:32 pm

saket wrote:Some questions may not necessary have correct answers ..... please see the old thread... :)


Saket, Thank you.

your statement definitely helps.

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