Suppose that the lifetimes of TV tubes are normally distributed with a
standard deviation of 1.1 years. Suppose also that exactly 30% of the tubes
die before 4 years. Find the mean lifetime of TV tubes. Carry your
intermediate computations to at least four decimal places. Round your answer
to at least one decimal place.

My question is: (a) how do you solve in excel for complement rule of P(X
or = 4.0).
(b) How do you solve a z-score of -0.2533 to produce a mean of 4.7787 in
excel?
I have tried to find a function or formula that I can use to determine
similar outcomes.

Okonita

I am a student taking a statistics class and I have this homeworks problems
to solve and I'll love to use excel to do this but don't know how?