Question 29.

What is defined by control limits?

A. A measuring instrument solely used to describe process capability. The process is found capable if the ±3 sigma range is exceeded by not more than 0.3% of a tested sample lot.

B. The limits of the six sigma area on either side of a control chart to plot measured values; data found outside the area are out of specification and can lead to rejection of an entire batch.

C. The area consisting of typically three standard deviations on either side of a mean value of a control chart to plot measured values found in statistical quality control

D. The area consisting of typically three standard deviations on either side of a mean value of a control chart to plot measured values found in quality assurance

## Oliver 75 - 29th Question

- jyotimayank
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- jyotimayank
- Expert

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iZenbridge Consultancy Pvt Ltd

### Re: Oliver 75 - 29th Question

The correct answer is C.

PMBOK® Guide Fifth Edition defines

For repetitive process, the control limits are generally set at +_ 3 sigma around a process variable X or process mean i.e. Centre Line. Upper control limit is drawn at 3 standard deviations above the process mean and lower control is drawn at 3 standard deviations below the centre line or process mean.

These limits are established to predict if process needs corrective action to bring process performance in line with needed stability and capability

Data points within +- 3 sigma are thought as “in Control”, and within acceptable limits excluding the rule of seven (described later).

Data points are within +-3 sigma means these data points are not crossing either of control limit. Anything beyond control limit requires investigation.

When 7 consecutive data points are presented on either side of mean, then “process is considered Out Control” based on heuristic of Rule of Seven.

Refer to Page 238-239 0f PMBOK® Guide 5th Edition

For more insight of this topic refer to the following blog

http://www.izenbridge.com/blog/control- ... lity-tool/

PMBOK® Guide Fifth Edition defines

**Control Limits**asUpper and lowerThe area composed of three standard deviations on either side of the centerline or mean of a normal distribution of data plotted on a control chart, which reflects the expected variation in the data.

**control limits**are established for the control chart and normally using statistical analysis or from historical records. Data points of a process are plotted to perform trend analysis toward either of control limits and with respect to centre line.For repetitive process, the control limits are generally set at +_ 3 sigma around a process variable X or process mean i.e. Centre Line. Upper control limit is drawn at 3 standard deviations above the process mean and lower control is drawn at 3 standard deviations below the centre line or process mean.

These limits are established to predict if process needs corrective action to bring process performance in line with needed stability and capability

Data points within +- 3 sigma are thought as “in Control”, and within acceptable limits excluding the rule of seven (described later).

Data points are within +-3 sigma means these data points are not crossing either of control limit. Anything beyond control limit requires investigation.

When 7 consecutive data points are presented on either side of mean, then “process is considered Out Control” based on heuristic of Rule of Seven.

Refer to Page 238-239 0f PMBOK® Guide 5th Edition

For more insight of this topic refer to the following blog

**Control Chart as a Component of Seven Basic Quality Tool**http://www.izenbridge.com/blog/control- ... lity-tool/

**Jyoti Gupta**

PMP Mentor & Coach

PMP Mentor & Coach

iZenbridge Consultancy Pvt Ltd