Marginal and
Conditional Probabilities
Marginal Probability Defination:
Marginal probability is the probability of a single event
without consideration of any other event. Marginal probability is also called
simple probability.
Mathematical Example:
Two ways classification of employee response with total-
|
|
In
Favor (A) |
Against
(B) |
Total |
|
Male
(M) |
15 |
45 |
60 |
|
Female
(F) |
4 |
36 |
40 |
|
Total |
19 |
81 |
100 |
P(Male)= 60/100= 0.60
P(Female)= 40/100= 0.40
P(In Favor)= 19/100= 0.19
P(Against)= 81/100= 0.81
Conditional Probability Defination:
Conditional probability is the probability that an event
will occur given that another event has already occurred.
Formula:
If A and B are two events then the conditional probability of A given B is written as-
and read as "the probability of A given that B has already occurred.
Mathematical Example:
Two ways classification of employee response with total-
|
|
In
Favor (A) |
Against
(B) |
Total |
|
Male
(M) |
15 |
45 |
60 |
|
Female
(F) |
4 |
36 |
40 |
|
Total |
19 |
81 |
100 |
P(In favor|Male) = 15/60 = 0.25
P(In favor|Female) = 4/40 = 0.10
P(Against|Male) = 45/60 = 0.75
P(Against|Female)
= 36/40 = 0.90
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