Combining Random Variables
AP Statistics · Flashcards · Recall
AP STATISTICS · FLASHCARDS
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QUESTION
What is the formula for the variance of the sum of two independent random variables
X
X
X
and
Y
Y
Y
?
QUESTION
What is the formula for the variance of a random variable
a
X
aX
a
X
?
QUESTION
What is the formula for the mean of the sum of two random variables
X
X
X
and
Y
Y
Y
?
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ANSWER
E
(
X
+
Y
)
=
E
(
X
)
+
E
(
Y
)
\text{E}(X + Y) = \text{E}(X) + \text{E}(Y)
E
(
X
+
Y
)
=
E
(
X
)
+
E
(
Y
)
. Expected value is linear, so sums distribute across expectations.
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