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?

Other than to do mutiplication, Excel is not needed to solve this problem.

First get a standard Z table and lookup either 30% or 70 % - doesn't matter
which since they are the same distance (in years) from the mean. Should be
something like .525?? Then multiply by the standard deviation to get the
distance (in years) to the mean. Call this distance Y. The mean is then 4+Y.
--
Gary's Student


"OKONITA" wrote:

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?