Answer:
a. 0.0001
b. 0.6561
c. 0.3439
d. B. The event in part (a) is unusual because its probability is less than or equal to 0.05.
Step-by-step explanation:
a. # We are given that the probability that a person in the United States has Type B+ blood = 0.10. Also we are told that four unrelated people in the United States are selected at random.
#We have to find here the probability that all four have type B+ blood.
Since the events are independent, we have :
Probability that all four have B+ blood = 0.10 x 0.10x 0.10x0.10
= 0.0001
Therefore, the probability that all four have type B+ blood is 0.0001
b. We have to find the probability that none have B+ blood. Using the complementary law of probability we have:
Probability that blood type is not B+ = 1 - 0.10= 0.90
Therefore, the probability that none have B+ blood
= 0.90 x 0.90 x 0.90x0.90=0.6561
Therefore, the probability that none have B+ blood is 0.6561
c. We have to find the probability that at least one of the four have B+ blood.
#The probability that at least one of the four have B+ blood = 1 - Probability that none have B+ blood type
=1-0.6561=0.3439
Therefore,the probability that at least one of the four has type B+ blood is 0.3439
d. An event is considered unusual if the probability of the event is small or less than 0.05 . We note that event a is the only small probabilty and is less than 0.05.
-a is thus considered unusual(the rest are all usual events)
