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A stock has an initial market price of $80. Exactly one year from now, its price will be given by: P = 80 * exp(i) where i is the rate of return. i is normally distributed with mean 0.2 and standard deviation 0.3. Construct a 95% confidence interval for the price of the stock after one year.
A
($54.27, $80)
B
($80, $175.91)
C
($54.27, $175.91)
D
($54.27, $140)
Explanation:
Given:
$80Step 1: Find 95% CI for i For a normal distribution, the 95% confidence interval is: CI = μ ± Z_{α/2} * σ where α = 0.05 Z_{0.025} = 1.96
CI for i = 0.2 ± 1.96 * 0.3 = 0.2 ± 0.588 = (-0.388, 0.788)
Step 2: Transform to CI for P
P = 80 * exp(i)
Lower bound: P_lower = 80 * exp(-0.388) = 80 * 0.6784 ≈ $54.27
Upper bound: P_upper = 80 * exp(0.788) = 80 * 2.1989 ≈ $175.91
Step 3: Final CI
95% CI for P = ($54.27, $175.91)
Key Points:
$54.27, $175.91)Why other options are incorrect:
$80$140 vs correct $175.91)