This set of Digital Communications Multiple Choice Questions & Answers (MCQs) focuses on “Random signals”.

1. Random variables give relationship between _____

a) Two random events

b) Probability of occurence of two random events

c) Random event and a real number

d) Random event and its probability of occurrence

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2. The distribution function of random variable is

a) P(X less than or equal to x)

b) P(X greater than or equal to x)

c) P(X less than x)

d) P(X greater than x)

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3. The distribution function of -(infinity) and (infinity) is _____

a) 0 and 1

b) 1 and 0

c) Both 0

d) Both 1

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4. The value of the probability density function of random variable is

a) Positive function

b) Negative function

c) Zero

d) One

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5. Which gives the measure of randomness of the random variable?

a) Mean

b) Variance

c) Standard variance

d) Pdf

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6. Random process is a function of ______

a) Random event and time

b) Random event and frequency

c) Random event and real number

d) None of the mentioned

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7. A random process is called as stationary in strict sense if

a) Its statistics vary with shift in time origin

b) Its statistics does not vary with shift in time origin

c) Its autocorrelation vary with shift in time

d) Its autocorrelation does not vary with shift in time

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8. For a stationary process, autocorrelation function depends on

a) Time

b) Time difference

c) Does not depend on time

d) None of the mentioned

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9. The autocorrelation function is maximum at

a) Origin

b) Infinity

c) Origin & Infinity

d) None of the mentioned

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10. Standard deviation is ______

a) Rms value of dc

b) Rms value or ac

c) Either ac or dc

d) Neither dc nor ac

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11. The average power of white noise is

a) Zero

b) Unity

c) Infinity

d) Between zero and one

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12. White noise has _____ mean and ______ variance.

a) Zero and zero

b) Finite and zero

c) Zero and finite

d) One and zero

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