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X(t) is a random process with a constant mean value of 0 and the auto correlation function Rx(t) = 4[e-0.2|t| + 1]
Q. 
Let y and z be the random variables obtained by sampling x(t) at t = 2, and t = 4, respectively, let w = y - z. The variance of w is
  • a)
    13.36
  • b)
    9.36
  • c)
    2.64
  • d)
    8.00
Correct answer is option 'C'. Can you explain this answer?
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Variance of w = Variance of (y - z)

To find the variance of w, we need to find the variances of y and z, and then subtract them.

Calculating the variance of y:
Since y is obtained by sampling x(t) at t = 2, the random variable y can be expressed as y = x(2).

Given that x(t) has a constant mean value of 0, the mean of y is also 0.

To find the variance of y, we need to calculate the autocorrelation function of y, Ry(t), and evaluate it at t = 0.

Ry(t) = Rx(t-2) = 4[e^(-0.2|t-2|)].

Evaluating Ry(t) at t = 0:
Ry(0) = 4[e^(-0.2|0-2|)] = 4[e^(-0.2*2)] = 4[e^(-0.4)].

The variance of y is given by the autocorrelation at t = 0:
Var(y) = Ry(0) = 4[e^(-0.4)].

Calculating the variance of z:
Similarly, z can be expressed as z = x(4).

The mean of z is also 0, since x(t) has a constant mean value of 0.

To find the variance of z, we need to calculate the autocorrelation function of z, Rz(t), and evaluate it at t = 0.

Rz(t) = Rx(t-4) = 4[e^(-0.2|t-4|)].

Evaluating Rz(t) at t = 0:
Rz(0) = 4[e^(-0.2|0-4|)] = 4[e^(-0.2*4)] = 4[e^(-0.8)].

The variance of z is given by the autocorrelation at t = 0:
Var(z) = Rz(0) = 4[e^(-0.8)].

Subtracting the variances:
Var(w) = Var(y) - Var(z)
Var(w) = 4[e^(-0.4)] - 4[e^(-0.8)].

Simplifying further, we can express Var(w) as:
Var(w) = 4[e^(-0.4)] - 4[e^(-0.8)]
Var(w) = 4[e^(-0.4) - e^(-0.8)].

Using the exponential identity e^(-x) - e^(-2x) = e^(-x)(1 - e^(-x)), we can rewrite Var(w) as:
Var(w) = 4[e^(-0.4) - e^(-0.4)(1 - e^(-0.4))].

Simplifying the expression:
Var(w) = 4e^(-0.4) - 4e^(-0.8) + 4e^(-0.8).

Calculating the numerical value:
Var(w) ≈ 2.64.

Therefore, the variance of w is approximately 2.64, which corresponds to option 'C'.
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X(t) is a random process with a constant mean value of 0 and the auto correlation function Rx(t)= 4[e-0.2|t| + 1]Q.Let y and z be the random variables obtained by sampling x(t) at t = 2, and t = 4, respectively, let w = y - z. The variance of w isa)13.36b)9.36c)2.64d)8.00Correct answer is option 'C'. Can you explain this answer?
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