Answer:
Option d is the right answer.
Step-by-step explanation:
Given that X, the life of a certain brand of battery is normally distributed, with mean 128 hours and standard deviation 16 hours.
Required probability = Prob that a battery you buy lasts at most 100 hours
=P(X<100)
Convert x into z
as
Z = [tex]\frac{100-128}{16} \\=-1.75[/tex]
Required proba
= [tex]P(X<100)\\=P(Z<-1.75)\\=1-P(Z>1.75)[/tex]
