# Statistical Quality Control Questions and Answers – Attribute Charts – Control Charts for Fraction Nonconforming – 1

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This set of Statistical Quality Control Multiple Choice Questions & Answers (MCQs) focuses on “Attribute Charts – Control Charts for Fraction Nonconforming – 1”.

1. Defectives word has almost same meaning as __________
a) Conforming
b) Nonconforming
c) Non-defective
d) Un-conforming

Explanation: A nonconforming item is an item which does not conform to the specifications defined for its quality characteristics. A defective is having almost same as the nonconforming item.

2. Quality characteristics which are related to only conforming or non conforming products, are called _________
a) Attributes
b) Continuous characteristics
c) Discrete characteristics
d) Variables

Explanation: The quality characteristics which are related to only conforming or non conforming products; are called attributes.

3. The control chart which relates to the fraction of defective product produced by a manufacturing process, is called _________
a) The control chart for nonconformities
b) Control charts for fraction nonconforming
c) Control charts for conformities per unit
d) Control chart for process mean

Explanation: The control charts which are related to the fraction of nonconforming or defective product produced by a manufacturing process is called the control chart for fraction nonconforming.

4. The control chart for fraction nonconforming is also called __________
a) u chart
b) c chart
c) p chart
d) R chart

Explanation: The control chart for fraction nonconforming is also called p chart. This chart is plotted for the fraction of nonconforming products produced by a manufacturing process.

5. The control chart designed to deal with the defects or nonconformities of a product, is called __________
a) p chart
b) c chart
c) R chart
d) s chart

Explanation: In some situations, it is more convenient to deal with the no of defects rather than the fraction nonconforming. The control charts designed for this purpose are called the c charts.

6. The c charts are also called _________
a) The control chart for nonconformities
b) Control charts for fraction nonconforming
c) Control charts for conformities per unit
d) Control chart for process mean

Explanation: The control charts which are made for the analysis of the defects in a product, are generally called the control charts for fraction nonconforming, or c charts.

7. The control charts used for the analysis of nonconformities per unit of a product, are called _________ charts
a) p
b) c
c) x
d) u

Explanation: The control charts useful in the situations where the average number of defects or conformities per unit, is more convenient basis for process control; are called the u charts.

8. The u charts are also called _________
a) The control chart for nonconformities
b) Control charts for fraction nonconforming
c) Control charts for conformities per unit
d) Control chart for process mean

Explanation: The control charts plotted for the conformities per unit are called u charts. They are helpful in the situations where average number of defectives is very important to determine process state.

9. The ratio of the number of nonconforming items in a population to total number of items in that population, is called _________
a) Fraction nonconforming
b) Fraction of nonconformities
c) Fraction of conformities per unit of product
d) Fraction of variability

Explanation: The fraction nonconforming is delineated by the ratio of nonconforming items in a population to the total number of items in the population.

10. The sample fraction nonconforming is expressed as __________
a) $$\hat{p}=\frac{2D}{n}$$
b) $$\hat{p}=\frac{D}{3n}$$
c) $$\hat{p}=\frac{D}{2n}$$
d) $$\hat{p}=\frac{D}{n}$$

Explanation: The sample fraction nonconforming is expressed by,
$$\hat{p}=\frac{D}{n}$$
Where D is nonconforming units and n is the sample size.

11. The center line of control chart of fraction nonconforming represents the value equal to ____________
a) Fraction nonconforming
b) Process mean
c) Process standard deviation
d) Sample mean

Explanation: The center line of the control chart of fraction nonconforming represents the value equal to the fraction nonconforming, i.e. the ratio between the number of nonconforming units to the total sample size.

12. If there are 9 items defective in the sample size of 28, what will be the value that the fraction nonconforming chart, will represent?
a) 0.2971
b) 0.3214
c) 0.6328
d) 0.8172

Explanation: The fraction nonconforming chart center line when standards are given, represents the value of fraction nonconforming which in this case, where m=1, D=9, n=28, is,
$$\bar{p}=\frac{[∑_{i=1}^m D_i]}{mn}=\frac{9}{28}$$=0.3214

13. If standards are not given, the estimate of the unknown fraction nonconforming of the process, is evaluated by formula ___________
a) $$\bar{p}=\frac{[∑_{i=1}^{m-1} D_i]}{m}$$
b) $$\bar{p}=\frac{[∑_{i=1}^{n-1} D_i]}{mn}$$
c) $$\bar{p}=\frac{[∑_{i=1}^{m} D_i]}{mn}$$
d) $$\bar{p}=\frac{[∑_{i=1}^{n} D_i]}{mn}$$

Explanation: The estimation of the process’ unknown fraction nonconforming is done by taking average of all the sample fraction nonconforming(s), i.e. $$\bar{p}$$
$$\bar{p}=\frac{[∑_{i=1}^{m} D_i]}{mn}$$

14. The fraction nonconforming says the same thing as the term defects per unit.
a) True
b) False

Explanation: Fraction nonconforming is the ratio of the number of defectives in a sample to its sample size. “Defects per unit” counts the defects in a single unit.

15. Variable control charts can also be applied on attributes but their efficiency will be less as compared to the attribute control charts.
a) True
b) False 