Statistics Problem

Question

A manufacturer knows that their items have a normally distributed lifespan, with a mean of 4.4 years, and standard deviation of 0.6 years.

If you randomly purchase 12 items, what is the probability that their mean life will be longer than 4 years?

Answer 1

I used the Geogebra Calculator Suite to help with this. Setting the mean parameter to

µ = 4.4 and the standard deviation to

σ = 0.6/√(12) asking for the right tail interval option marked with a [ symbol.

Asking for P( 4 <= X ) gave 0.9895393323311

Hope that helps!