Ok maybe I'm not thinking clearly enough but here's the question with a stupid story to make it sound realistic:
Q) The fluorescent light tubes made by the company "Well-lit" have lifetimes which are normally distributed with mean 2010 hours and standard deviation 20 hours. The company decides to promote its sales of the tubes by guaranteeing a minimum life of the tubes, replacing free of charge any tubes that fail to meet this minimum life.
If the company wishes to have to replace free only 3% of the tubes sold, find the guaranteed minimum it must set.
I've tried to make sense of the wording but I'm too slow to do that!
So I know that
I think I need to do something with the 3% in order to get a number value which I can put into this equation:
I'm just really confused with all the information; we've learnt how to do questions in stats but now they're in real life situations and it can get a tad confusing.
I know I'm not as good as everyone here but I just need some help with this question