# Industrial Engineering Questions and Answers – Statistical Quality Control Basics

This set of Industrial Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Statistical Quality Control Basics”.

1. Chance variation is also called as ____________
a) Usual variation
b) Unusual variation
c) Assignable cause variation
d) Causal variation

Explanation: Chance variation is also known as usual variation. The operator has no control over it. It occurs in a random way. For example, random fluctuation in voltage at the time of enlargement in photography may produce a poor quality print. One cannot avoid these variations.

2. __________ is also called as unusual variation.
a) Usual variation
b) Unusual variation
c) Assignable cause variation
d) Causal variation

Explanation: Assignable cause variation is also known as unusual variation. Causes of the variation can be traced and steps can be taken to rectify these causes. Variation due to assignable causes can be of greater magnitude.

3. Variables data is also called as ___________
a) Continuous data
b) Attributes data
c) Discrete data
d) Intermittent data

Explanation: Variable data is measurable data and can be any value over a certain interval. Example of variable data is the dimensions of the part measured, the hardness of the surface, the temperature in degrees centigrade, weight in Kgs. The values in the data are in decimal form.

4. _________ is also called as discrete data.
a) Continuous data
b) Attributes data
c) Discrete data
d) Intermittent data

Explanation: The data obtained by counting is known as attribute data. It is also called as discrete data. For example, an inspection of products using Go and No Go gauges gives discrete data. Discrete data can only be in integer form. It cannot be in decimal form.

5. The shape of the normal distribution curve is __________
a) Bell shape
b) Crescent shape
c) s – shape
d) Trefoil shape

Explanation: Normal distribution curve is in bell shape. It is symmetrical about its mean value. The curve is considered between x ± 3σ limits. But theoretically, it extends from –α + 0σ.

6. Percentage of the total area covered under the normal distribution curve for the specification limits x ± 0.6745 σ is ___________
a) 68.26
b) 99.73
c) 95.46
d) 50

Explanation: The area under the normal distribution curve within the limits -0.6745σ to +0.6745σ is 50% i.e., is 50% of the area under the curve falls within the limits of x ± 0.6745σ.

7. The formula for the standard deviate (z) is given by ___________
a) z = $$\frac {(x_1 * \overline{x})}{\sigma }$$
b) z = $$\frac {(x_1 – \overline{x})}{\sigma }$$
c) z = $$\frac {(x_1 + \overline{x})}{\sigma }$$
d) z = $$\frac {(\overline{x} – x_1)}{\sigma }$$

Explanation: The standard deviate (z) is given by z = $$\frac {(x_1 – \overline{x})}{\sigma }$$
Where
x1 is the value of the variable, x is the mean value of x and σ is the standard deviation of x.

8. Which of the following is an example of variable charts?
a) x – chart only
b) R chart only
c) Both x – chart and R chart
d) P chart only

Explanation: To plot, interpret and analyze variable data, variable charts are used. Both x and R charts are examples of variable data.

9. __________ are examples of control charts for attribute data.
a) x – chart and np chart
b) P, np and 100p charts
c) Both x – chart and R chart
d) R chart and P chart

Explanation: P, np and 100p charts are used to plot, interpret and analyze attributes data. x and R charts are used to plot, interpret and analyze variable data. Charts that can be plotted using discrete data are known as attributes charts. Hence, P, np and 100p charts are examples of attribute data.

10. Go and No Go gauges are used to collect discrete data.
a) True
b) False

Explanation: The data collected through inspection by using Go and No Go gauges is not by the direct measurement of the actual dimensions of the product. Inspection through Go and No Go gauges is an indirect method of Inspection. Hence the products inspected are either accepted or rejected. As the value of deviation / error cannot be specified, the data is an attribute or discrete data.

Sanfoundry Global Education & Learning Series – Industrial Engineering.

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