Robert Klassen Manufacturing, a medical equipmentmanufacturer, subjected 90 heart pacemakers to 5,000 hours of testing. Halfway through the testing,4 pacemakers failed.   Percent of failures:
Number of failures per unit-hour of operating time:
Number of failures per unit-year:

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

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