Exercise · ZW-EXPONENTIAL-DISTRIBUTION-002 · ★☆☆ Basic
If \(X\) is exponential with \(\lambda=3\), find \(\operatorname{Var}(X)\).
Choose one option.
Show answer
- A. \(\tfrac19\)
Explanation
The variance is \(1/\lambda^2=1/9\); \(1/3\) would be the standard deviation.
Review the concept: Exponential distribution
An exponential variable measures the waiting time until the first event of a memoryless process that occurs at a constant rate \(\lambda\); \(f\) is its density.
\[f(x)=\lambda e^{-\lambda x},\quad x\ge0\]
More practice problems: exponential distribution
- ZW-EXPONENTIAL-DISTRIBUTION-001 If X is exponential with λ=2, find E[X].
- ZW-EXPONENTIAL-DISTRIBUTION-003 If X is exponential with λ=1, find P(X>2).
- ZW-EXPONENTIAL-DISTRIBUTION-004 If X is exponential with λ=2, find P(X≤ 1).
- ZW-EXPONENTIAL-DISTRIBUTION-005 The mean time between failures of a machine is 5 hours and is exponential. What is λ?
- ZW-EXPONENTIAL-DISTRIBUTION-006 If X is exponential with mean 3, find P(X>6).
- ZW-EXPONENTIAL-DISTRIBUTION-007 If X is exponential with λ=1, find P(X>3| X>1).
- ZW-EXPONENTIAL-DISTRIBUTION-008 If X is exponential with λ=2, find P(1<X<2).
- ZW-EXPONENTIAL-DISTRIBUTION-009 If X is exponential with λ=2, what is its median?
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