Metal components for a machine have lengths which are normally distributed with mean 8 cm and standard deviation 4 cm.

Question

A) the longest 10% of components require filling down. What is the smallest length of component which require filing down?

B) the shortest 15% of components have to be discarded. What is the smallest length of component which would not be discarded?

Please help

Thankyou

Answer 1

you can answer these and many other Z table things at

http://davidmlane.com/hyperstat/z_table.html

Answer 2

3(a)X=Z×sd
X=85+(1.2816)x4
X=90.1264