Question 1160975
a. 50%, since E(X bar)=8 minutes

z=(x bar-mean)/sigma/sqrt(n)
sigma/sqrt(n)=2/2=1
so b is looking at 8 and 10 minutes with sd 1
this is z between 0 and 2, which is 0.4772.

for 16 now the sd will be 2/sqrt(16)=0.5
and the same probability of 0.4772 will occur. 

It is much more likely that the sampling distribution will be narrower and distances from the expected value of 8 (in this instance) won't be as much as the sample size increases.