Question 1100921
The middle 80% is the 10th and 90th percentiles
10th percentile is z=-1.28; 90th is +1.28
z=(x-mean)/sd
1.28=(x-9.3)/4.2
x-9.3=5.38
x=14.68
-1.28=(x-9.3)/4.2
x=3.92
(3.9, 14.68) units are years