# Industrial Engineering Questions and Answers – Reliability-Cost Analysis

This set of Industrial Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Reliability-Cost Analysis”.

1. Which of the following distributions assume constant failure rate?
a) Exponential distribution
b) Weibull distribution
c) Normal distribution
d) Lognormal distribution

Explanation: Exponential distribution assumes a constant failure rate (defined with the symbol ‘λ’). It is most commonly used distributions in reliability.

2. Which of the following mathematical equation is correct to calculate the reliability (R) in exponential distribution?
a) R(t) = e-λt
b) R(t) = eλt
c) R(t) = e1-λt
d) R(t) = e1+λt

Explanation: Let R(t) be the reliability at a given instant of time, λ be the failure rate, t be the time, then according to the exponential distribution, the reliability R(t) = e-λt.

3. What is the reliability of the component after three hours when the failure rate is 10%?
a) 0.756
b) 0.741
c) 0.714
d) 0.792

Explanation: Given,
Failure rate, λ = 10% = 0.1 per hour
Time = t = 3 hours
Reliability = R(t) = e-λt = e-0.1 × 3 = 0.741

4. Reliability is the probability of a system, component or a product that performs its intended function for a given time under the given working conditions.
a) False
b) True

Explanation: Reliability is the probability of a system, component or a product that performs its intended function for a given time under the given working conditions. Reliability measures the performance of the system or an item.

5. Which of the following is not a phase in the bath-tub curve?
a) Early failure
b) Constant failure
c) Wear out failure
d) High failure

Explanation: Bath-tub curve represents the pattern of failure for many products. It is divided into three phases. They are:
i. Early failure or Infant mortality or debugging stage
ii. Constant failure or useful life
iii. Wear-out stage or End of life failure

6. Which of the following is the first stage of the bath-tub curve?
a) Early failure
b) Constant failure
c) Wear out failure
d) High failure

Explanation: Bath-tub curve represents the pattern of failure for many products. It is divided into three phases namely, early failure, constant failure and wear-out failure. Early failure or Infant mortality stage is the starting stage in the bath-tub curve.

7. Which of the following is the second stage of the bath-tub curve?
a) Early failure
b) Constant failure
c) Wear out failure
d) High failure

Explanation: Bath-tub curve represents the pattern of failure for many products. It is divided into three phases namely, early failure, constant failure and wear-out failure. Constant failure is the middle stage in the bath-tub curve. Failure rate remains constant during this period.

8. Which of the following is the last stage of the bath-tub curve?
a) Early failure
b) Constant failure
c) Wear out failure
d) High failure

Explanation: Bath-tub curve represents the pattern of failure for many products. It is divided into three phases namely, early failure, constant failure and wear-out failure. Wear out failure is the last stage in the bath-tub curve.

9. Which of the following stage of the bath-tub curve has a constant failure rate?
a) Early failure
b) Random failure zone
c) Wear out failure
d) High failure

Explanation: Random failure zone which is the second zone of the bath-tub curve has a constant failure rate. This is the middle stage in the failure pattern curve, also called the bath-tub curve.

10. Failure cost increases as the reliability of the item or the system increases.
a) True
b) False

Explanation: Failure cost decrease as the reliability of the item increases. If the reliability of the item increases, the probability of failure decreases i.e., failure rate decreases.

Sanfoundry Global Education & Learning Series – Industrial Engineering.

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