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# s1 Q watch

1. Two events, R and S are independant. P(R|S) = 3/4 and
P(S ) = P(S'nR'). By letting x equal P(S ) and forming an
equation for x, or otherwise, find:
(a ) P(S )
(b ) P(S'nR)
(c ) P(S|R)

thanks
2. If two events A and B are independent, the following three pairs of events are also independent:

A' and B
A and B'
A' and B'

--

Since R and S are independent, P(R) = P(R | S) = 3/4.

x
= P(S)
= P(S' n R')
= P(S')P(R') . . . . . since S' and R' are independent
= (1 - x)(1/4)

(5/4)x = (1/4)
x = 1/5

P(S) = 1/5

P(S' n R)
= P(S')P(R) . . . . . since S' and R are independent
= (4/5)(3/4)
= 3/5

P(S | R)
= P(S) . . . . . since S and R are independent
= 1/5

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