Answer and Explanation:
The computation is shown below:
a. For the percentage of failures is
= Number of failures ÷ number of pacemakers tested
= 4 ÷ 90
= 4.4%
b. For Number of failures per unit-hour of operating time
= Number of failure ÷ total time - non-operating time
= 4 ÷ (5,000 × 90) - (5,000 ÷ 2 × 4)
= 4 ÷ (450,000 - 10,000)
= 4 ÷ 440,000
= 9.09 × 10^-6
= 0.00000909 failure per unit-hour
c. For Number of failures per unit-year is
= Failure ÷ unit year
= 0.0000090909 × 24 hours × 365 days
= 0.07963 failure per unit-year
