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JNTU B.Tech II PROBABILITY THEORY AND STOCHASTIC PROCESSES Previous Question Paper (October - 2020 - R15)

B.Tech | II | I | R15 | October - 2020

Answer PaperPaper Code: 123BTMaximum Marks: 75Time: 2 hours

Answer any five questions. All questions carry equal marks.

Main

115 marks
a

State and prove Bayes theorem of probability.

8 marks

Answer

Bayes' theorem states that for a set of mutually exclusive and collectively exhaustive events B1, B2, ..., Bn that partition the sample space, the conditional probability of an event Bi given that event A has occurred is given by:

P(Bi|A) = (P(A|Bi)P(Bi)) / (Σ P(A|Bj)P(Bj))

To prove this, start with the definition of conditional probability for any two events A and Bi:

P(A ∩ Bi) = P(A|Bi)P(Bi) = P(Bi|A)P(A)

Rearranging for P(Bi|A) gives:

P(Bi|A) = (P(A|Bi)P(Bi)) / P(A)

Since the events Bj form a partition of the sample space, the event A can be expressed as the union of disjoint events (A ∩ Bj). By the law of total probability, P(A) is:

P(A) = Σ P(A ∩ Bj) = Σ P(A|Bj)P(Bj)

Substituting this expression for P(A) into the conditional probability formula yields the final theorem.

b

Find the probability of the card being either red or a king when one card is drawn from a regular deck of 52 cards.

7 marks

Answer

Let A be the event that the card is red, and B be the event that the card is a king. A standard deck has 52 cards.

1. The number of red cards is 26, so P(A) = 26/52.

2. The number of kings is 4, so P(B) = 4/52.

3. The intersection (A ∩ B) represents red kings. There are 2 red kings (King of Hearts and King of Diamonds), so P(A ∩ B) = 2/52.

Using the addition rule for probabilities:

P(A ∪ B) = P(A) + P(B) - P(A ∩ B)
P(A ∪ B) = 26/52 + 4/52 - 2/52 = 28/52

Simplifying the fraction, the probability is 7/13 or approximately 0.538.

215 marks
a

Given P(A) = 1/3, P(B) = 1/2, P(A∩B) = 1/5, then find P(AUB) and P(Ac ∩ Bc).

8 marks

Answer

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b

Differentiate between the joint probability and conditional probability.

7 marks

Answer

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315 marks
a

The mean of Binomial distribution is 3 and the variance is 9/4. Find i) The value of n ii) P(x > 7).

8 marks

Answer

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b

Describe the properties of moment generating function.

7 marks

Answer

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4

Mention about the characteristics of the Gaussian and Rayleigh density Functions and with their distributions graphs in detail.

15 marks

Answer

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5

Mention about the Statistical Independence and Show that the variance of a weighted sum of uncorrelated random variables equal the weighted sum of the Variances of the random Variables.

15 marks

Answer

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615 marks
a

Discuss the Joint Central Moments.

7 marks

Answer

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b

If X and Y are two random variables which are Gaussian. If a random Variable Z is defined as Z=X+Y, Find fZ(Z).

8 marks

Answer

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715 marks
a

Distinguish between the Ergodic and Mean-Ergodic Processes.

7 marks

Answer

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b

Show that PSD and auto correlation function of random process form a Fourier transform pair.

8 marks

Answer

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8

A WSS random process x(t) is applied to the input of an LTI system whose impulse response is 5t e-2t. The mean of x(t) is 3. Find the output of the system.

15 marks

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