Answer:
(a) z(105)= (105-95)/10
= 1
z(85)= (85-95)/10
= -1
P(85< x < 105) = P(-1< z < 1) = 0.6825
Quantity of people of 1600 that have IQ between 85 and 115 = 0.6825*1600= 1092
(b) z(105) = (115-95)/10 = 2
z(85) = (75-95)/10 = -2
P(-2< z < 2) = 0.6827
quantity of people of 1600 that have IQ between 75 and 115 = 0.6825x1600=1092
(c) Z(>125)=( 125-100)/10=3
