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Mutually exclusive and exclusive

  1. Sep 19, 2003 #1
    currently, im studying probability in my school.

    i'm bit confused with the difference btw :-
    (a) mutually exclusive and exclusive
    (b) independent and mutually exclusive.

    anyone can explain?
     
  2. jcsd
  3. Sep 19, 2003 #2

    mathman

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    (a) I'm not sure what you are trying to describe.
    (b) Mutually exclusive - the probability that both will happen is 0.
    Independent - probability that both will happen is the product of the probabilities of the individual events.
     
  4. Sep 20, 2003 #3

    HallsofIvy

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    I'm with mathedman. I have never heard the term "exclusive" used in probability except as part of "mutually exclusive". I would be inclined to say that "exclusive" and "mutually exclusive" are the same thing.

    As mathedman said: if two events are "mutually exclusive" then the probability of both happening is 0 (P(A and B)= 0). If they are independent, P(A and B)= P(A)*P(B).
     
  5. Sep 24, 2003 #4

    hypnagogue

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    Or, in linguistic terms:

    If two events are mutually exclusive, then it is impossible for both to happen-- the occurence of one necessarily excludes any chance that the other occurs.

    If two events are independent, then they do not influence eachother-- the occurence of one does not change the probability that the other will happen.

    For instance, let
    A: the event that I leave my house to go to my 9-5 job today
    B: the event that I sleep in my house until 5pm today
    C: the event that someone calls my home phone number
    D: the event that a coin flip comes up heads

    A and B are mutually exclusive events, since if I sleep until 5pm I can't go to work that day, and likewise if I go to work then I must have been awake before 5pm. A and C are not mutually exclusive, since going to work does not exclude the possibility that someone places a call to my home phone, and vice versa.

    A and D are independent events, since my going to work does not affect the chance that a coin flip comes up heads, and vice versa (assuming I'm not fatalistic enough to base my decisions on a coin toss, of course). However, B and C are not independent events, since if I sleep until 5pm, my sleepiness affects a greater chance that someone (my overly demanding employer, for one ) will call my house to see what's going on.

    Actually, it is useful to think of mutual exclusion and independence as exact opposite relations. If two events X and Y are independent, then knowing that X occurs gives you absolutely no relevant information as to the probability of Y occuring. On the other hand, if X and Y are mutually exclusive, then knowing that X occurs gives you complete information as to the probability of Y occuring, since you know that there is no chance that Y can occur.
     
    Last edited: Sep 24, 2003
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