It has been shown that 30% of a certain group of people own a pet. Find the probability that, among nine of these people, at least 2 own a pet.

The probability that, among nine of these people, at least 2 own a pet is ___. (Round to three decimal places as needed.)


Answer:
Given:

Probability of success $(p)=0.30$

Sample size $(n)=9$

Solution:
The probability that among nine of these people at least 2 own a pet:
$$ \text{P}(x \geq 2) = \sum_{2}^{9} \binom{n}{x} \cdot p^x \cdot (1-p)^{n-x} $$ $$ = \sum_{2}^{9} \binom{9}{x} \cdot 0.30^x \cdot (1-0.30)^{9-x} $$ $$ = 0.804$$

Final Answer:
The probability that among nine of these people at least 2 own a pet $=0.804$

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