Question

The diameter of an electric cable is normally distributed with mean 0.8 and variance 0.0004. A cable is considered defective if the diameter differs from its mean by more than 0.025. Find the probability of obtaining defective cables.

Make use of the following values

◊ (0.025) = 0.51, ◊ (1.25) = 0.8944, ◊(0.8) =0.7881

Answer 1

The standard deviation is 0.02.
P (X>0.825 and X< 0.775) (two tailed)& = 2P(X>0.825) = 2P (Z > 0.025/0.02) = 2P (Z > 1.25)& = 0.2113