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Topic: disjointness
Replies: 9   Last Post: Dec 8, 1999 1:35 PM

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Ruth Carver

Posts: 33
Registered: 12/3/04
disjointness
Posted: Dec 6, 1999 5:31 PM
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I'm having difficulty explaining why disjoint events are not
independent. YMM states, "If A and B are disjoint, then the fact that
A occurs means B cannot occur. So disjoint events are not
independent." I'm ok with the first part but I'm having difficulty
coming up with an example to show that disjoint events are not
independent.

Al Reif wrote
<Disjoint events cannot occur simultaneously. When rolling a die, you
<could roll a 3 [Event A] or roll a 4 [Event B]. But you cannot
roll a 3 and a 4 at the same time with one die. In contrast, rolling
a 3 <[EventA] and having blonde hair [Event B] are not disjoint--they
can happen at the same time.

But isn't rolling a 3 or a 4 on a die independent?

Thanks.
Ruth Carver
Germantown Academy
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