Question

A compact disc is designed to last an average of 4 years with a standard deviation of 0.8 years. What is the probability that a CD will last less than 3 years?

Answer 1

To compute for the probability value of P-value, we need to see first as to how is 3 years from the given mean value. So, for this case we have (3 - 4) = 1 below the standard deviation of 0.8. Thus, the z -score for this would me z < -1/0.8 = -1.25. Given a z-score of z < -1.25. Using the table chart for the P-values, we have P(z < -1.25) = 0.1056. Meaning there is a 10.56% chance that a CD will last for less than 3 years. Thus, probability is 10.56%.