Answer: 0.2612736
Round this value however you need to.
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Explanation:
- n = 7 = sample size
- p = 0.60 = probability of someone being in favor
- k = 5 = number of people in favor
We use the binomial distribution here. The formula for that is
P(k) = (n C k)*(p)^k*(1-p)^(n-k)
where the n C k refers to the nCr combination formula
[tex]_n C _r = \frac{n!}{r!*(n-r)!}[/tex]
simply replace r with k.
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So,
P(k) = (n C k)*(p)^k*(1-p)^(n-k)
P(5) = (7 C 5)*(0.6)^5*(1-0.6)^(7-5)
P(5) = 21*(0.6)^5*(0.4)^(2)
P(5) = 21*0.07776*0.16
P(5) = 0.2612736
This decimal value is exact (meaning there aren't any other digits after that last '6'). Round this value however you need to.
There's roughly a 26.1% chance of getting exactly 5 people to be in favor of the project.