Suppose we have four boxes. A, B, C and D containing coloured marbles as given below:
One of the boxes has been selected at random and a single marble is drawn from it. If the marble is red, what is the probability that it was drawn from box A?, box B?, box C?
Let R be the event of drawing the red marble.
Let EA, EB, and EC respectively denote the events of selecting the box A, B, and C.
Total number of marbles = 40
Number of red marbles = 15
`:.P(R) = 15/40 =3/8`
Probability of drawing the red marble from box A is given by P (EA|R).
Probability that the red marble is from box B is P (EB|R).
Probability that the red marble is from box C is P (EC|R).