1 A system is to be composed of 5 identical components in se

1. A system is to be composed of 5 identical components in series. What is the lowest reliability component that can be used in order to have an overall system reliability of 0.90?

2. A project consists of four activities, each of which has a variance of 1. The project standard deviation is: A. 1 B. 2 C. 3 D. 4 E. 16

Solution

1.

Let P = the lowest probebility

Thus, as they should all work,

P^5 = 0.90

Thus, taking the fifth root,

P = 0.90^(1/5) = 0.979148362 [ANSWER]

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2.

The variances add up, so

var(x1+x2+x3+x4) = 1+1+1+1 = 4

Thus, the standard devaition is

s(x1+x2+x3+x4) = sqrt(4) = 2 [ANSWER, B]