Question

A compact disc is designed to last an average of 4 years with a standard deviation of 0.8 years.

Answer 1

3-4/.8=1.25
then use the probability z chart to get
10.56%

Answer 2

Answer:

10.56%

Step-by-step explanation:

Step 1: Use the z formula  

The z-formula is

$z=\frac{x-mean}{standard | deviation}$

$z=\frac{3-4}{0.8} \\\\z=\frac{-1}{0.8} \\\\=-1.25$

P(z < -1.25)  

Step 2: Use a p chart to find -1.25

-1.25 on a p chart is .1056

there is a 10.56% chance that a CD will last less than 3 years.

The answer is 10.56%