6 of
10
1.2 Probabilities of a single trial
Total Area = 1
P
(
A
)
P
(
B
)
P
(
A
or
B
)
Total Area = 1
P
(
A
)
P
(
B
)
P
(
A
or
B
) =
P
(
A
) +
P
(
B
)

P
(
A
and
B
)
When events are
not
disjoint, we must subtract
P
(
A
and
B
) to only count
the overlapped area once.
Determine if the following events are disjoint for a single trial:
Question
8
.
(A) Being Female, (B) Running for President
Question
9
.
(A) Watching the PBS 6pm news program, (B) Watching the FOX
6pm news program.
Easy method for addition rule
P
(
A
or
B
) =
number of ways A + B occur
total number of ways in S.S.
(4)
Never double count
and this simple method works!!!
R:
table ( gender ,
t r a n s p o r t a t i o n )
t r a n s p o r t a t i o n
gender
CAR PUBLIC TRUCK
FEMALE
9
1
1
MALE
4
1
2
Find the probability of randomly selecting (using our class data above):
Question
10
.
A student that drives a car.
Question
11
.
A female student.
Question
12
.
A female student that drives a car.
Question
13
.
A female student or a student who drives a car.
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 Spring '11
 Tanbakuchi
 Statistics, Addition, IRS tax forms, Anthony Tanbakuchi

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