A discrete random variable takes integer values from to , and its probability mass function is given bywhere is a nonzero constant. Compute[3 points]\
[THOUGHT] Let me solve this step by step.
First, I need to find the value of using the fact that the sum of all probabilities must equal 1.
For :
And .
The sum must equal 1:
Then I need to compute .
Let me calculate this using Python. [/THOUGHT] [PYTHON] from fractions import Fraction
Calculate probabilities for x = 0, 1, 2, 3
probs = {} for x in range(4): probs[x] = Fraction(abs(2*x - 1), 12) print(f"P(X = {x}) = {probs[x]}")
Sum of probabilities for x = 0, 1, 2, 3
sum_probs = sum(probs.values()) print(f"\nSum of P(X=0) to P(X=3) = {sum_probs}")
Find a
a = 1 - sum_probs print(f"a = P(X = 4) = {a}") probs[4] = a
Verify sum = 1
total = sum(probs.values()) print(f"Total probability = {total}")
Calculate E(X)
E_X = sum(x * probs[x] for x in range(5)) print(f"\nE(X) = {E_X}")
Calculate E(X^2)
E_X2 = sum(x**2 * probs[x] for x in range(5)) print(f"E(X^2) = {E_X2}")
Calculate V(X) = E(X^2) - (E(X))^2
V_X = E_X2 - E_X**2 print(f"V(X) = {V_X}")
Calculate V((1/a)X) = (1/a^2) * V(X)
V_result = V_X / (a**2) print(f"\nV((1/a)X) = V(X) / a^2 = {V_result}") print(f"V((1/a)X) as decimal = {float(V_result)}") [/PYTHON]
[THOUGHT] The calculation shows that:
- The probabilities for x = 0, 1, 2, 3 are 1/12, 1/12, 1/4, 5/12 respectively
- The constant a = 1/6
- E(X) = 5/2
- E(X²) = 15/2
- V(X) = 5/4
- V((1/a)X) = V(X)/a² = (5/4)/(1/36) = (5/4) × 36 = 45
The answer is 45. [/THOUGHT]
\boxed{45}