In testing a new vaccine, researchers found that 30% of all patients using it will have a mild side effect. A random sample of 20 patients using the vaccine is selected. Find the probability that more than 8 patients will have this mild side effect.

The probability that more than 8 patients will have this mild side effect is _. (Round to three decimal places as needed.)


Answer:
Given:

Probability of success $(p)=0.30$

Sample size $(n)=20$

Solution:
The probability that more than 8 patients will have this mild side effect:
$\text{P}(x > 8) = \sum_{9}^{20} \binom{n}{x} \cdot p^x \cdot (1-p)^{n-x} = \sum_{9}^{20} \binom{20}{x} \cdot 0.30^x \cdot (1-0.30)^{20-x} = 0.1133$

Final Answer:
The probability that more than 8 patients will have this mild side effect $=0.1133$

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