1. If a control chart shows a process in statistical control, you can be certain

Question

1. If a control chart shows a process in statistical control, you can be certain that all special causes have been completely eliminated. (True/False)

2. The sample sizes when using control charts for attributes are commonly much larger usually in the hundreds than the samples of size four or five usually used in control charts for variables. (True/False)

3. A control chart is a graphic device for describing the variation in a sample statistic over time. (True/False)

4. When preparing Shewhart X¯ and R control charts, samples sizes of _____ are usually sufficient.

a. 1-2

b. 4-5

c. 7-8

d. >10

5. Common or random causes typically make up about _____ of process problems.

a. 15%

b. 30%

c. 50%

d. 85%

6. The average run length (ARL) is the average number of points plotted on a control chart before a point falls outside the control limits, indicating the process is out of control. (True/False)

7. A process that is operating without any assignable causes present is said to be in-control. (True/False)

8. Both random and assignable causes of variation are inherent parts of every process. (True/False)

9. The most frequently used attribute control chart is the _____ chart, which is used when we are interested in controlling the fraction of units that do not conform to the specifications. (True/False)

10. The X¯ chart is used to monitor the process average and an R chart can be used to monitor process variability. (True/False)

11. The in-control average run length (ARL) for an X¯ control chart with 3-sigma control limits is ______?

a. 370

b. 470

c. 570

d. None of the above

12. Specification limits are useful in helping determine where to set the limits on a control chart. (True/False)

13. Which of the following is NOT one of the Western Electric rules for determining nonrandom patterns on control charts?

a. Ten consecutive points plot on one side of the center line

b. Four out of five consecutive points plot at a distance of 1-sigma or beyond from the center line

c. Seven successive points run either upward or downward

d. Two out of three consecutive points plot beyond a two-sigma limit

14. The usual distance of the control limits from the center line on a Shewhart control chart is three times the standard deviation of the statistic plotted on the chart.(True/False)

Explanation / Answer

1. FALSE

Explanation: There may chance of nonrandom patterns on a control chart which indicate the presence of special-cause variation.

2. TRUE

3.FALSE

Explanation: A control chart is a graphical tool, that uses actual variation in observed data to determine if a process is "in control" or "out of control".

4.d. >10

Hope this will be helpful. Thanks and God Bless You.

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