This set of Statistical Quality Control Multiple Choice Questions & Answers (MCQs) focuses on “The Cumulative Sum Control Chart – 4”.
Explanation: The tabular cusum works by accumulating derivations from mean that are above target with one statistic Ci+, which is called one sided upper cusum. It is expressed as,
Explanation: The tabular cusum works also by accumulating derivations from the mean that are below the target with one statistic Ci–. The value of this value is called the one sided lower cusum and its expressed as,
3. What is K called in the expressions of the one-sided Cusums?
a) Regarded value
b) Related value
c) Resultant value
d) Reference value
Explanation: The values of the statistics used in the construction of a tabular cusum are called one sided upper and lower Cusums. K is used in their expressions which is called Reference value.
4. Which of these is another name of the reference value?
a) Regarding value
b) Stoppage value
c) Stack value
d) Assignable value
Explanation: The constant K in the expression of the one-sided Cusums, is called the reference value. It is also called slack value, or allowance.
5. The value of the reference value is chosen ____________
a) 3/4 ways between mean and the out-of-control mean towards the mean
b) 1/2 ways between mean and the out-of-control mean
c) 3/4 ways between mean and the out-of-control mean towards the out-of-control mean
d) 1/4 ways between mean and the out-of-control mean towards the mean
Explanation: The value of the reference value or K is chosen such that, it stay halfway between the target mean and the out-of-control value of the mean, that we are interested in finding out quickly.
6. What is the value δ is called, when used in the expression of K?
a) The shift of mean in standard deviation units
b) The shift of variance in standard deviation units
c) The shift of standard deviation in mean units
d) The shift of mean in variance units
Explanation: The value δ is used in the expression of K or the reference value.
Here this value δ is called the shift of mean in standard deviation units.
Explanation: The value μ1 is called the out-of-control mean. It is the value of mean when process changes its state to out-of-control. Its value is,
Explanation: The value K is called the allowance. This is used in the one-sided upper and lower Cusums expressions. It is expressed as,
9. What is the starting value of one-sided upper cusum?
Explanation: The one-sided upper cusum is expressed as follows,
The starting value of this would be C0+ which is always taken as 0.
10. What is the starting value of the one-sided lower cusum?
Explanation: The lower one sided cusum is expressed as follows,
This value is called the starting value of lower one-sided cusum when the value of i=0. The value of C0–=0.
Explanation: We know that,
So, as the value of quantity becomes negative, it becomes lesser than 0. So we take the maximum value between zero and it, i.e. Ci–=0
Explanation: As the value of Ci– is chosen as the maximum between zero and quantity , we always have Ci–≥0.
13. After the value of Ci– increasing than the value of _____ the process is said to be out-of-control.
a) Control interval
b) Decision interval
c) Distribution interval
d) Calculation interval
Explanation: There is a certain value decided for both Ci– and Ci+, after increasing from which, the process is said to be out-of-control. It is called decision interval.
14. If the value of μ0 > μ1, K will have a negative value.
15. The generally used value of K is the only value, which substantially impact the performance of the cusum.
Explanation: The cusum performance not only depends on the allowance or reference value K, but it also depends on the decision interval H. It is because H is related to the value of Ci+ or Ci– above which the process becomes out-of-control.
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