Question 857133
A survey report states that 42% of adults visit their doctor regularly. Suppose that 10 adults are selected at random. 

a) what is the probability that exactly 9 adults visit their doctor regularly in such group? 

probability = {{{(matrix(2,1,10,9))(0.42^9)(0.58)}}} = {{{highlight(0.0024)}}}

b) find the mean and standard deviation for the number of adults that visit their doctor regularly in such group of 10 adults. 
mean = np = 10(0.42) = {{{highlight(4.2)}}}
standard deviation = {{{sqrt(npq)}}} = {{{sqrt(10*0.42*(1-0.42))}}} = {{{highlight(1.5608)}}}

c) Is it unusual to have 9 or more adults that visit their doctor regularly in such group of 10 adults? explain

P(X ≥ 9) =  {{{(matrix(2,1,10,9))(0.42^9)(0.58^1)}}} +  {{{(matrix(2,1,10,10))(0.42^10)(0.58^0)}}} = {{{highlight(0.0025)}}}
It is unusual because the probability is less than 0.05.