The probability that at least one of them has been vaccinated is 0.9866.
There are only two conceivable outcomes for each individual. They are either immunized or they are not. A person's likelihood of receiving a vaccination is unrelated to anyone else. Therefore, to answer this query, we employ the binomial probability distribution.
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
P( X = x ) = Cₙ,ₓ × pˣ × ( 1 - p )ⁿ ⁻ ˣ
In which Cₙ,ₓ is the number of different combinations of x objects from a set of n elements, given by the following formula.
Cₙ,ₓ = n! / x!( n - x )! and p is the probability of X happening.
Now, 66% of the people have been vaccinated.
Therefore, p = 0.66
If 4 people are randomly selected.
Then the probability that at least one of them has been vaccinated will be:
P( X ≥ 1 ) when n = 4
So,
P( X ≥ 1 ) = 1 - P( X = 0 )
Now,
P( X = x ) = Cₙ,ₓ × pˣ × ( 1 - p )ⁿ ⁻ ˣ
P( X = 0 ) = C₄,₀ · ( 0.66 )⁰ · ( 1 - 0.66 )⁴
P( X = 0 ) = 0.01336336
P( X ≥ 1 ) = 1 - P( X = 0 ) = 1 - 0.01336336 = 0.98663664
0.9866 probability that at least one of them has been vaccinated.
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