Stat 427
NAME____
solutions
_____________________
Exam 1
Professor Berliner; WI 2011
Exam Score:
_______/100 points
Part I Score:
_______
/
40 points
Fillin the blanks:
Each question is worth 4 points (no partial credit)
1.
The _
sample space
____ of an experiment is the set of all possible
outcomes of that experiment.
2.
If
A
and
B
are disjoint (mutually exclusive) events, then the probability of
both events occurring simultaneously is equal to __
zero
____________.
3.
If
P
(
A
) = .50,
P(B
) = .70, and
, then
___
.80
____.
4.
If P
(
A
) =
.35,
P
(
B
) = .50 and
.20, then
P
(
A

B
) is _
2/5=.40
_.
5.
If
.123 and
P
(
A

B
) = .60, then
P
(
B
) is
_
.123/.60=.205
__.
6.
If
P
(
A
) = .25,
P
(
B
) = .40, and events
A
and
B
are independent, then
_
.25 (.40) = .10
___________.
7.
If
P
(
A
) =.60,
P
(
B
) = .40, and events
A
and
B
are independent, then
P
(
A

B
) is
__
.60
________.
8.
The probability mass function
p
(
x
) of a discrete random variable
X
is
p
(
0
) = .15,
p
(1) = .30,
p
(2) = .20,
p
(3) = .10, and
p
(4) = .25.
The value of
the cumulative distribution function
F
(
x
) at x = 2 is ____
.65
______.
9.
If the expected value of a discrete random variable
X
is
E
(
X
) = 5, then
E
(2
X
+ 3) is ___
13
_______.
10.
Let
X
be a discrete random variable with
E
(
X
) = 4.5 and
E(X
2
)
= 26.25, then
the variance of
X
is
V
(
X
) = __
6
________.
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 Spring '08
 Staff
 Probability, Probability mass function

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