Question

The life of a blood pressure monitor has a normal distribution with an average of 40 years and a standard deviation of one year. What should the warranty be to replace a malfunctioning monitor with - if the company does not want to replace more than 1% of all the monitor.

Thank you in Advance!

Answer 1

Normal distribution table give μ+2.33σ as the 99% level.
Calculate the warranty period accordingly.

Tell me which brand it is that has 40 years mean life! :)

Answer 2

Try z-scores:

z = (x - mean)/sd

Your data:

2.33 = (x - 40)/1

Solve for x.

Note: 2.33 represents the z-score corresponding to the 1% in your problem.