This set of Statistical Quality Control Multiple Choice Questions & Answers focuses on “Control Charts for x̅ and R – 2”.

1. LCL for the R chart is given by ____

a) D_{3} R

b) D_{2} R

c) R – D_{3} R

d) d_{2} R

View Answer

Explanation: LCL for an R chart is always given by the following equation,

LCL = D

_{3}R.

2. In the general equation of UCL of a control chart, for any x chart, which of these is used as the estimator of μ?

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3. Which of these gives the correct value of A_{2} used in the equation for control limits of a x control chart?

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Explanation: The value of A

_{2}used in the equation of control limits of a x control chart is given by following equation,

4. In phase I application of x and R chart, the control limits obtained from the equations are treated as ______

a) Final limits

b) Trial limits

c) Warning limits

d) Pattern limits

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Explanation: The obtained limits from the equation of control limits for a x and R chart, are generally treated as Trial limits. They allow us to determine whether the process was in control when the m initial samples were taken.

5. Which term is having a closest meaning as Sampling Distributions?

a) Control charts

b) On site inspection

c) Whole lot inspection

d) Acceptance sampling

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Explanation: The term “control charts” is having a closest meaning to “sampling distribution” because, control charts are also plotted on the data obtained from the sample inspection and also, they show variation in sample data.

6. Process capability generally uses ____

a) Specifications

b) Control Limits

c) Process standard deviation

d) Mean of any one sample

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Explanation: Process capability studies make use of the specifications of any certain Critical-to-quality characteristic or quality characteristic to estimate the performance of any process.

7. The process standard deviation is given by ____

a) R/d_{2}

b) Rd_{2}

c) 1/d_{2}

d) R/d

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Explanation: The process standard deviation may be estimated by using the following equation,

8. For any process, the sample ranges are, 1.2,1.5,1.1,1.4,1.5. The subgroup size is 5. What will be the process standard deviation? Given: d_{2}=2.326 and A_{2}=0.577

a) 0.576

b) 2.322

c) 0.511

d) 2.463

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9. A tolerance diagram is also called ____

a) Scatter diagram

b) Defect concentration diagram

c) Histogram

d) Tier chart

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Explanation: The run chart of individual observations in each sample is called the tolerance diagram for any process. The tolerance diagram is also called Tier chart of the process.

10. Is there any relationship between specification limits and control limits of x and R charts?

a) Yes, Specification limits = Control limits

b) Yes, Control limits=Specification limits/2

c) No

d) Yes, Control limits*0.5 = Specification limits

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Explanation: There is no certain relationship defined; between the control limits of x and R charts and the specification limits of any quality characteristic.

11. Control limits are ___

a) Limits defined by customers

b) Limits driven by the natural variability of the process

c) Limits driven by the inherent variability of the process

d) Statistical limits

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Explanation: The control limits are the limits for a quality characteristic for a process to be in-control. They are driven by the natural variability of the process.

12. The natural variability of the process is measured by ____

a) Process mean

b) Sample standard deviation

c) Process standard deviation

d) Sample mean

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Explanation: The natural variability of any process is the main factor affecting the control limits of any quality characteristic while plotting a control chart. They are measured by process standard deviation, σ.

13. What type of chart will be used to plot the number of defectives in the output of any process?

a) x bar chart

b) R chart

c) c chart

d) p chart

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Explanation: The number of defectives in the samples of the output of a process is monitored by the p chart and the number of defects is monitored by a “c chart”.

14. Process standard deviation is necessarily equal to the sample standard deviation of the same process.

a) True

b) False

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Explanation: It is not necessary that the sample standard deviation will always be equal to the process standard deviation, for a same process. This is because; there may be assignable causes of variation while the sample is being produced by the process.

15.“There is no need of revision of control limits once calculated by the equations of control limits.

a) True

b) False

View Answer

Explanation: In the phase I application of control charts, the limits calculated from equations are used as trial limits because it gives us a idea about the variation, both, inherent and natural. So with time the variation changes, to compensate this, limits must be revised after a certain time.

**Sanfoundry Global Education & Learning Series – Statistical Quality Control.**

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