Question

How can you rewrite P(z £ –1.75) in order to find the answer? P(z £ 1.75) P(z ³ -1.75) 1 - P(z £ -1.75) 1 - P(z £ 1.75)

Answer 1

Option d is the right answer.

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 =
`(100-128)/(16) \\=-1.75`

Required proba

=
`P(X<100)\\=P(Z<-1.75)\\=1-P(Z>1.75)`