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A control chart shows that the last 8 frames produced were all a little less then the average weight. You know you need to action this because the:

control chart violates the:

A. rules of seven

B. rules of eight.

C. Standard deviation rule.

D.3-sigma rule.

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Question added by Muhammad Farooq , QA-QC MANAGER , AL Bawani contracting co.
Date Posted: 2016/10/01
Mohamed Ezzdin
by Mohamed Ezzdin , QHSE manager , Ostool Transport Co.

We have8 control chart rules listed in the table below. If we have any case of the ones below we should take an action

 

 Control Chart Rules

Rule

Rule Name

Pattern

1

Beyond Limits

One or more points beyond the control limits

2

Zone A

2 out of3 consecutive points in Zone A or beyond

3

Zone B

4 out of5 consecutive points in Zone B or beyond

4

Zone C

7 or more consecutive points on one side of the average (in Zone C or beyond)

5

Trend

7 consecutive points trending up or trending down

6

Mixture

8 consecutive points with no points in Zone C

7

Stratification

consecutive points in Zone C

8

Over-control

consecutive points alternating up and down

 

 

 

The control chart and its zones are shown in below diagram

 

 

 

In our case in this question we have8 consecutive points on one side of the average in zone c which violates the rule its name ZONE C which is number4 in the table. This is considered a small shift in the process and can be maintained with little adjustments.