Statistical Quality Control Questions and Answers – Modeling Process Quality -Continuous Distributions – 1

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This set of Statistical Quality Control Multiple Choice Questions & Answers (MCQs) focuses on “Modeling Process Quality -Continuous Distributions – 1”.

1. Which of these cannot be shown on the continuous distributions?
a) Length dimension measurement of a box
b) Volume measurement of the box
c) Area measurement of one face of the box
d) Number of defects on the surface of the box
View Answer

Answer: d
Explanation: Continuous distributions are used to describe the variation in the values of variables which are continuous, i.e. which take values on continuous scale. Number of defects is discrete not continuous parameter.
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2. Which of these is a continuous distribution?
a) Pascal distribution
b) Lognormal distribution
c) Binomial distribution
d) Hyper geometric distribution
View Answer

Answer: b
Explanation: Pascal, binomial, and hyper geometric distributions are all part of discrete distribution which are used to describe variation of attributes. Lognormal distribution is a continuous distribution used to describe variation of the continuous variables.

3. Which of these distributions has an appearance of bell-shaped or unimodal curve?
a) Lognormal distributions
b) Normal distribution
c) Exponential distribution
d) Cumulative exponential distributions
View Answer

Answer: b
Explanation: Out of all continuous distributions, Normal distributions are the only distributions, which have a shape of curve as a bell. The curves of them are mostly unimodal.

4. The rule of multiplication of probability is possible only ____
a) When events are independent
b) When events are mutually exclusive
c) When events are Bayesian
d) When events are Empirical
View Answer

Answer: a
Explanation: The rule of multiplication of probability is possible only when the events are independent.
P(A and B)=P(A).P(B)

5. Which of these equations describe the normal continuous distribution?
a) \(f(x)=\frac{1}{\sigma \sqrt{2π}} e^{-0.5(\frac{x-μ}{σ})^2}, -\infty < x < -\infty\)
b) \(f(x)=\frac{1}{\sqrt{2π}} e^{-0.5(\frac{x-μ}{σ})^2}, -\infty < x < -\infty\)
c) \(f(x)=\frac{1}{\sigma \sqrt{π}} e^{-0.5(\frac{x-μ}{σ})^x}, -\infty < x < -\infty\)
d) \(f(x)=\frac{1}{\sigma \sqrt{2π}} e^{-0.5(\frac{x-μ}{σ})^x}, -\infty < x < -\infty\)
View Answer

Answer: a
Explanation: Normal distribution is a part of continuous distributions, which is described by the following equation,
\(f(x)=\frac{1}{\sigma \sqrt{2π}} e^{-0.5(\frac{x-μ}{σ})^2}, -\infty < x < -\infty\)
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6. “ϕ(∙)” is said to be cumulative distribution function of _________
a) Standard binomial distribution
b) Standard normal distribution
c) Standard exponential distribution
d) Standard gamma distribution
View Answer

Answer: b
Explanation: For the standard normal distribution, “ϕ(∙)” is described as the cumulative distribution function, which has the value of mean equal to zero and the corresponding standard deviation equal to unity.

7. The probability that the normal random variable x is less than or equal to some value a is said to be the _____
a) Standard normal distribution
b) Lognormal distribution
c) Exponential distribution
d) Cumulative normal distribution
View Answer

Answer: d
Explanation: The normal distribution has several important special cases, out of which, the cumulative normal distribution is defined as the probability that the normal random variable x≤a.

8. Which of these is true for the normal distributions?
a) \(μ_y = a_1 μ_1 + a_2 μ_2 +⋯+ a_n μ_n\)
b) \(μ_y = a_1 μ_1^2 + a_2 μ_2^2 +⋯+ a_n μ_n^2\)
c) \(μ_y^2 = a_1^2 μ_1^2 + a_2^2 μ_2^2 +⋯+ a_n^2 μ_n^2\)
d) \(σ_y^2 = a_1^2 σ_1^2 + a_2^2 σ_2^2 +⋯+ a_n^2 σ_n^2\)
View Answer

Answer: a
Explanation: From property, for any normal distribution which has,
\(y = a_1^2 x_1 + a_2^2 x_2 +⋯+ a_n^2 x_n\)
We have,
\(μ_y = a_1 μ_1 + a_2 μ_2 +⋯+ a_n μ_n\)

9. The central limit theorem is true for _______ distribution.
a) Normal distribution
b) Lognormal distribution
c) Exponential distribution
d) Gamma distribution
View Answer

Answer: a
Explanation: The central limit theorem uses an assumption that, the normal distribution is an appropriate distribution for a random variable. That’s why; the central limit theorem is true only for Normal distribution.
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10. If a variable x is having its value equal to the exponential function of another variable w, i.e. “x=exp⁡(w)”, and w has normal distribution; the distribution of x is called _______
a) Normal distribution
b) Exponential distribution
c) Lognormal distribution
d) Gamma distribution
View Answer

Answer: c
Explanation: For a random variable x, which has “x=exp⁡(w)” where w is having a normal distribution; the distribution of such a random variable x, is said to be the Lognormal distribution. It is a continuous distribution.

11. For a lognormal random variable, what is the value of mean?
a) \(μ=e^{\theta+\frac{w^2}{2}}\)
b) \(μ=e^{\frac{w^2+\theta}{2}}\)
c) \(μ=e^{w+\frac{\theta^2}{2}}\)
d) \(μ=e^{\theta+w^2}\)
View Answer

Answer: a
Explanation: if for x, which has x=ew, and w has a normal distribution with mean θ and variance w2; x is a lognormal random variable with mean expressed as
μ=e(θ+ w2/2).

12. The exponential distribution is given by _____
a) f(x)=xeλ
b) f(x)= e-λx
c) f(x)= λe-λx
d) f(x)=ew
View Answer

Answer: c
Explanation: The continuous probability distribution is said to be exponential if the distribution follows this equation,
f(x)= λe-λx.

13. The cumulative distribution function for the lognormal distribution is given by _____
a) \(\phi[\frac{ln⁡(a)-\theta}{\omega}]\)
b) \(\phi[\frac{ln⁡(a)-\theta}{a}]\)
c) \(\phi[\frac{ln⁡(a)-\omega}{\omega}]\)
d) \(\phi[\frac{ln⁡(a)-\theta}{\theta}]\)
View Answer

Answer: a
Explanation: The lognormal cumulative distribution function defines the probability that the variable x is less than or equal to a is given by,
\(\phi[\frac{ln⁡(a)-\theta}{\omega}]\)
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14. If a card is chosen from a deck of cards, what is the probability that it is either 7 or 9?
a) 4/52
b) 7/52
c) 9/52
d) 8/52
View Answer

Answer: d
Explanation: There are 8 cards in the deck which are either 7 or 9. There are total 52 cards in the deck, so the probability that the card is either a 7 or a 9 is 8/52; based upon the outcomes of interest divided by the total possible outcomes.

15. The rule of multiplication of probability is possible only _____________
a) When events are independent
b) When events are mutually exclusive
c) When events are Bayesian
d) When events are Empirical
View Answer

Answer: a
Explanation: The rule of multiplication of probability is possible only when the events are independent.
P(A and B)=P(A).P(B)

Sanfoundry Global Education & Learning Series – Statistical Quality Control.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn