In a recent survey, 80% of the community favored building a health center in their neighborhood. if 15 citizens are chosen, what is the mean number favoring the health center?

The formula to discover the sample mean is: = ( Σ xi ) / n.All that formula is saying is add together all of the statistics in your data set ( Σ means “add up” and xi means “all the numbers in the data set).
But the only given is the 80% and 15. Therefore, Mean = total number x probability 
= 15 x 0.8 = 12 The answer is 12