The probability that the tenth person randomly interviewed in that city is the fifth one to own a dog = 0.051
Given,
Consider the interview of a person is a trial.
Lets consider it success if a person owns a dog and consequently , a person without a dog will be a failure.'
Let the random variable X represent the number of persons to be interviewed to get 5 dog owner: in other words, to get 5 successors.
Probability of a success in each trial is p = 0.3. Therefore probability of a failure in each trial is q = 1 - p = 0.7 .
Because trials are independent. X has a negative binomial distribution with parameters k = 5, p = 0.3
P(X =x ) = b(x: k, p) =
where, x = k , k + 1 , k + 2......(1)
Now, Lets find the probability that the tenth person randomly interviewed in that city is the fifth one to own a dog
Using equation (1), we get:
P(X = 10) = b(10: 5, 0.3)
= [(10-1) (5 - 1)]
= [(9)(4)]
= 0.05146
Hence, The probability that the tenth person randomly interviewed in that city is the fifth one to own a dog = 0.051
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