Independent vs Mutually Exclusive

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Homework Help Overview

The discussion revolves around the concepts of independence and mutual exclusivity in probability theory, specifically in the context of introductory statistics. The original poster is seeking clarification on whether events that are "not independent" must be mutually exclusive.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand the relationship between independence and mutual exclusivity, questioning if the absence of independence implies mutual exclusivity. Other participants provide definitions and examples to clarify these concepts, including the distinction between independent events and mutually exclusive events.

Discussion Status

Participants are actively engaging with the concepts, providing definitions and examples to illustrate the differences between independent and mutually exclusive events. There is a recognition that while mutually exclusive events cannot be independent, the reverse is not necessarily true, leading to a nuanced exploration of the topic.

Contextual Notes

The discussion is framed within the context of introductory statistics, and participants are careful to reference definitions and examples relevant to the subject matter. There is an emphasis on understanding the implications of the definitions rather than arriving at a definitive conclusion.

lovemake1
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Homework Statement



If a question states event A and B are "not" independent, does it mean that they are Mutually Exclusive?
My brain is having hard time accepting that if they are not dependent, then they don't neccesarily have to be 'dependent'. Kinda like if its not hot, then its cold. it can still be warm.
any help clearing this confusion is greatly appreciated.

This is introductory statistics, so nothing crazy has been introduced.

Homework Equations


The Attempt at a Solution

 
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If a question states event A and B are "not" independent, does it mean that they are Mutually Exclusive?
No.

Events A and B are independent if the outcome of one does not effect the outcome of the other... P(A|B)=P(A)

Events are mutually exclusive if having one event means you cannot have the other... P(A|B)=0

Being mutually exclusive is one way that events can be dependent ... but not the only way.
See HallsofIvy (below).
 
Last edited:
For example, suppose you roll a single die. Event A is "you roll a number larger than 3". Event B is "you roll and even number" We can write event A as {4, 5, 6}. We can write event B as {2, 4, 6}. The probabilities of both event A and event B are 3/6= 1/2. The numbers that are both "larger than 3 and even" are {2, 6} so the probability that "you roll a number than is both larger than 3 and even" is 2/6= 1/3. That is NOT (1/2)(1/2)= 1/4 so these events are not independent. But it is not 0 so they are not "mutually excusive"
 
lovemake1 said:

Homework Statement



If a question states event A and B are "not" independent, does it mean that they are Mutually Exclusive?
It's interesting to note that the converse of this statement IS true. If two events are mutually exclusive, then they cannot be independent unless one of them has probability zero. This follows immediately from the definitions of mutually exclusive: P(A \cap B) = 0 and of independent: P(A \cap B) = P(A) P(B).
 
Just to clarify jbunniii:
If two events A and B are mutually exclusive, then they are not independent - but it is not true to say that "if A and B are not independent, it means that they are Mutually Exclusive".All dogs are animals but not all animals are dogs.
 

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