Choose the best answer

1		A system is composed of three components. All three must function in order for the system to work. Each one has a reliability of .90. System reliability is:
			A)	.729
			B)	.900
			C)	.990
			D)	.999
			E)	2.700.
2		A system is composed of three components, I, II, III. The reliabilities of the three components are respectively 0.50, 0.90, and 0.90. III is a standby for II that switches on only if II fails. The overall system reliability is:
			A)	2.300
			B)	.405
			C)	.495
			D)	.860
			E)	.540
3		A machine can operate for an average of 99 hours before needing service. Service time averages one hour. The availability of the machine is:
			A)	1.00
			B)	.99
			C)	.98
			D)	.97
			E)	none of these.
4		If the MTBF increases and the expected repair time remains the same, availability will:
			A)	decrease
			B)	remain the same
			C)	increase
			D)	impossible to say
5		Which of the following describes the negative exponential distribution as a model of service lives?
			A)	It requires the z statistic.
			B)	Reliability is the area to the left of the MTBF.
			C)	It is symmetrical.
			D)	Reliability is the area to the right of the MTBF.
			E)	It has an infinite area.