Question

What must be true in order for P (A or B) = P(A) + P (B)?

A and B cannot be disjoint.
A and B must be independent.
A and B cannot be independent.
A and B must be disjoint.
It is always true.

Answer 1

you can add the probabilities of the events are disjoint, i.e. they cannot happen at the same time

Answer 2

so my answer would be d? that they must be disjoint? @satellite73

Answer 3

*if the events are disjoint

Answer 4

yup

Answer 5

Thnak you! :)

Answer 6

\[P(A\cup B)=P(A)+P(B)-P(A\cap B)\] if the events are disjoint, then \(P(A\cap B)=0\) and you are left with \[P(A\cup B)=P(A)+P(B)\]

Answer 7

yw