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The lifetime in months of a certain part has a gamma distribution with = = 2. A company
Chapter 5, Problem 5.3-18(choose chapter or problem)
The lifetime in months of a certain part has a gamma distribution with = = 2. A company buys three such parts and uses one until it fails, replacing it with a second part. When the latter fails, it is replaced by the third part. What are the mean and the variance of the total lifetime (the sum of the lifetimes of the three parts) associated with this situation?
Questions & Answers
QUESTION:
The lifetime in months of a certain part has a gamma distribution with = = 2. A company buys three such parts and uses one until it fails, replacing it with a second part. When the latter fails, it is replaced by the third part. What are the mean and the variance of the total lifetime (the sum of the lifetimes of the three parts) associated with this situation?
ANSWER:Step 1 of 2
Given: Gamma distribution of
Let us assume that the three bought parts are independent. Each of these parts has the distribution of
The mean of a gamma distribution is the product of its parameters:
The variance of a gamma distribution is the product of and the square of :