Page 45 - Probability, Random Variables and Random Processes

CHAP. 1) PROBABILITY

There are 100 patients in a hospital with a certain disease. Of these, 10 are selected to undergo a drug
treatment that increases the percentage cured rate from 50 percent to 75 percent. What is the probability
that the patient received a drug treatment if the patient is known to be cured?
Ans. 0.143

Two boys and two girls enter a music hall and take four seats at random in a row. What is the probability
that the girls take the two end seats?
Ans.
Let A and B be two independent events in S. It is known that I'(A n B) = 0.16 and P(A u B) = 0.64. Find
P(A) and P(B).
Ans. P(A) = P(B) = 0.4

The relay network shown in Fig. 1-18 operates if and only if there is a closed path of relays from left to
right. Assume that relays fail independently and that the probability of failure of each relay is as shown.
What is the probability that the relay network operates?
Ans. 0.865

I 0.3 I

Fig. 1-18