In a large metropolitan area, the probabilities are .87, .36, .30 that a family (randomly chosen for a sample survey) owns a colour television set, a black and white television set, or both kinds of sets. What is the probability that a family owns either anyone or both kinds of sets?
Let us consider that,
E1 be the element that a family owns a colour TV & E2 be the event that a family owns black & white TV.
Now P(E1) = 0.87 & P(E2) = 0.36 …….. (given)
& P (E1 ∩ E2) = 0.30
To find: probability that the family owns either anyone or both kinds of sets.
Now, by the general rule –
P (A U B) = P(A) + P(B) – P(A ∩ B)
We have,
P (E1 U E2) = P(E1) + P(E2) – P(E1 ∩ E2)
= 0.87 + 0.36 – 0.30
= 1.23 – 0.30
= 0.93
Therefore, 0.93 is the required probability