Answer:
The answer is [tex]\frac{1}{256}[/tex]
Step-by-step explanation:
If we assume that people cannot taste a difference between bottled water, then the probability of identifying tap water is 0.5
Thus, P(identify tap water)=0.5
The probability that at least 8 of the 9 people identify the tap water correctly is the sum of the probabilities
Since P(identify tap water)=0.5 each probabilities are the same and equal to
[tex]0.5^9[/tex] =[tex]\frac{1}{512}[/tex]
So we have [tex]2*\frac{1}{512}[/tex] = [tex]\frac{1}{256}[/tex]