Psy 207
Erwin Segal
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Source for probability examples
  Men Women
TOTAL
A
14
24
38 
B
24
36
60
C
24
34
58
D
12
20
32
F
6
6
12
TOTAL
80
120
200
Sample space is selecting one individual from this class of 200 students

P(A)=38/200=.19
P(B)=60/200=.3
P(B|M)=24/80=P(BM)/P(M)=.12/.40=.3
P(M|B)=24/60=P(BM)/P(B)=.12/.30=.4
P(B|W)=36/120=P(BW)/P(W)=.18/.60=.3
P(BM)=24/200=P(B)P(M)=.3*.4=.12; B and M are independent, no other variables are
P(A+B)=P(A)+P(B)-P(AB)=.19+.30=.49
P(A+M)=P(A)+P(M)-P(AM)=.19+.40-.07=.52
P(MC)=24/200=.12
P(AB)=0  A and B are mutually exclusive, as are all of the grades with one another
P(A|M)=14/80=P(AM)/P(M)=.07/.4=.175
P(A|W)=24/120=P(AW)/P(W)=.12/.60=.20

Sample space is rolling a pair of dice
                                        DIE1                SUM OF TWO DICE

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DIE2>
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Events can be partitioned as the sum of the two numbers of points.
Events can be partitioned as the number of one spots occurring