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By: Neil E. Cotter |
Probability |
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Linear combinations rV's |
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Example 4 |
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Ex: Given X~u(0, 1), (i.e., X is uniformly distributed from 0 to 1), and Y = 5X + 1, find the following values:
a) μY.
b) .
Sol'n: a) The mean of Y is given by a standard formula:
Substituting values given in the problem, we have the following result:
The mean value of X is 1/2 since it has a uniform distribution on (0, 1). Making this substitution gives our answer:
b) The covariance, , is defined in terms of E(XY):
If we substitute Y = 5X + 1, we are left with only expected values involving x:
Using the result from (a), the second term simplifies as follows:
The first term becomes a sum:
To find the expected value of X2, we consider the variance of X. For a uniform distribution on (0, 1), the variance is 1/12.
Solving for E(X2), we have the following:
Substituting this result in our earlier equation, we have the information needed to complete the calculation of covariance:
and