Solution: To evaluate for P(0.372<x<0.428) we shall proceed as follows: z-score is given by: z=(x-μ)/σ thus when x=0.372: z=(0.372-0.4)/0.028 z=-1 thus P(x<0.372)=P(z<-1)=0.1587
when x=0.428 z=(0.428-0.4)/(0.028)=1 P(x<0.428)=P(z<1)=0.8413 thus P(0.372<x<0.428) =P(z<1)-P(z<-1)=0.8413-0.1587=0.6826
