Finding the control limits used in the range control chart

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Reference no: EM13104123

1. Computer upgrades have a nominal time of 80 minutes. Samples of 10 observations each have been taken, and the results are as listed. Historical data show that the standard deviation of the upgrade times is 0.5 minutes.

	Sample 1	Sample 2	Sample 3	Sample 4	Sample 5
Observation 1	79.2	80.5	79.6	78.9	79.7
Observation 2	78.8	78.7	79.6	79.4	80.6
Observation 3	80.0	81.0	80.4	79.7	80.5
Observation 4	78.4	80.4	80.3	79.4	80.0
Observation 5	81.0	80.1	80.8	80.6	81.1
Observation 6	77.8	78.8	80.4	77.7	79.8
Observation 7	79.3	79.6	79.4	80.6	81.0
Observation 8	80.4	80.5	78.7	80.8	80.6
Observation 9	81.1	79.4	81.3	81.0	80.8
Observation 10	80.9	80.2	80.5	79.2	77.9
Sample Mean, X-bar	79.69	79.92	80.1	79.73	80.20

What are the 3-sigma (z= 3) control limits to be used in the mean (X-bar) control chart and what is the decision based on this X-bar chart?

A) Control Limits = (79.33,81.13) Decision = Process is out of control
B) Control Limits = (78.50,81.42) Decision = Process is in control
C) Control Limits = (78.88,80.18) Decision = Process is out of control
D) Control Limits = (79.45,80.40) Decision = Process is in control

Computer upgrades have a nominal time of 80 minutes. Samples of 10 observations each have been taken, and the results are as listed. Historical data show that the standard deviation of the upgrade times is 0.5 minutes.

	Sample 1	Sample 2	Sample 3	Sample 4	Sample 5
Observation 1	79.2	80.5	79.6	78.9	79.7
Observation 2	78.8	78.7	79.6	79.4	80.6
Observation 3	80.0	81.0	80.4	79.7	80.5
Observation 4	78.4	80.4	80.3	79.4	80.0
Observation 5	81.0	80.1	80.8	80.6	81.1
Observation 6	77.8	78.8	80.4	77.7	79.8
Observation 7	79.3	79.6	79.4	80.6	81.0
Observation 8	80.4	80.5	78.7	80.8	80.6
Observation 9	81.1	79.4	81.3	81.0	80.8
Observation 10	80.9	80.2	80.5	79.2	77.9
Sample Range	3.3	2.3	2.6	3.4	3.2

What are the control limits to be used in the Range (R) control chart and what is the decision based on this R chart?

A) Control Limits=(0.45,3.20) Decision=Out of control
B) Control Limits=(0.65,5.27) Decision=In control
C) Control Limits=(2.3, 3.4) Decision= In control
D) Control Limits=(0.74, 5.45) Decision= In control

Fixing a quality problem will often cost money; to minimize these costs it is best to find and fix the problem _______.

Which one of the following statements is incorrect about quality control activities, inspection and control charts?A) High-cost, low-volume items often require careful inspection since we make them so infrequently.
B) The optimum level of inspection minimizes the sum of inspection costs and the cost of passing defectives.
C) The purpose of control charts is to distinguish between random variation and assignable variation in the process
D) The optimum level of inspection occurs when we catch at least 98.6 percent of the defects.
E) A time-ordered plot of sample statistics is called a control chart.

Reference no: EM13104123

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