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Quality and Reliability

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I need assistance in writing 500-600 words on quality and reliability - they are related concepts but are fundamentally different in a number of ways. Discuss them.

Vishnu Vandana

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Software Reliability is one of the most important aspects of software quality. Software reliability is a quality characteristic which quantifies the operational profile of a system.

Software engineers need accurate quality assessment of the software under development. Early prediction of fault prone components is of particular interest for software developers to quickly find defects and deliver more reliable software products. Software quality prediction focuses on identifying fault prone modules (procedures), while software reliability prediction aims at quantifying the probability that a program will execute without failure since its start time.

Software quality models aim at predicting critical software components prior to testing. They are generally built from metrics collected in past projects or releases, and are used to identify fault prone modules in the current project/release and subject them to more rigorous verification activities. Successful models are characterized by high prediction accuracy, thus allowing software developers to quickly identify defects early in the software life cycle. Automated detection of fault prone modules during software development process is an important prerequisite for developing reliable large systems.

Software reliability is a statistical measure of how well software operates with respect to its requirements. There are two related software engineering research issues about reliability requirements. The first issue is achieving the necessary reliability, i.e., choosing and employing appropriate software engineering techniques in system design and implementation. The second issue is the assessment of reliability as a method of assurance that precedes system deployment.

There are many indirect software reliability assessment approaches, aiming at predicting software reliability in early life cycle. Most of them are, however, not accurate enough for reliable predictions. In addition, many of them are statistically dependent.

Software Quality Models
Studies show that many modeling techniques have been developed and applied for software quality prediction. These include:
- Logistic regression ,
- Discriminant analysis ,
- The discriminative power techniques,
- Optimized Set Reduction,
- Artificial neural network,
- Fuzzy classification,
- Bayesian Belief Networks (BBNs),
- Genetic algorithms, and
- Classification trees .

It was shown that the prediction accuracy of these models does not vary significantly. A trade-off can be achieved by having a higher defect detection rate and compromising the overall prediction accuracy, or vise versa. Thus, a performance comparison of various models, if based on only ...

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1. Another issue ABC is facing is reliability of their products, in part because they are manufacturing increasingly complex products. One such product is designed and manufactured with five different subassemblies combined in series. It was determined through testing that those subassemblies have reliabilities, which are R1, R2, R3, R4, and R5; of .997, .998, .995, .999, and .990, respectively (refer to the Question 3 Flowchart). ABC's president has asked you what the reliability of the overall product (RP) is, given those subassembly reliabilities utilized in series.

• Analyze this operations management issue.
• Provide the algebraic equation (using RP, R1, R2, R3, R4, and R5 as variables) for this analysis.
• Calculate and provide the overall product reliability, given those subassemblies utilized in series.

2. ABC's president has also asked you what the overall reliability of a different product (RP) is. That product has four subcomponents (SC1, SC2, SC3, and SC4). The components are organized as SC1, followed by SC2 in parallel with SC3, which are then both followed by SC4 (refer to the Question 4 Diagram). Their respective reliabilities are SC1R=.97, SC2R=.98, SC3R=.95, and SC4R=.93.

• Analyze this operations management issue.
• Provide the algebraic equation (using RP, SC1R, SC2R, SC3R, and SC4R as variables) for this analysis.
• Calculate and provide the overall product reliability given those subassemblies.

3. ABC Manufacturing is also concerned about the quality of its manufacturing processes. One of the products the company sells is a bottle of liquid lubricant associated with the pump product line. ABC's president is familiar with the operations management concept of control limits (determining an upper and lower numerical threshold such that a process is considered in control as long as it stays within those limits).

The president has asked you to take samples of the amount of liquid in those bottles and determine the upper control limit (UCL) and lower control limit (LCL) of three standard deviations. He told you that, based on previous testing, the standard deviation (SD) for this process is 0.035. You took sample measurements of the volume of liquid in the bottles, done at different times of the day (in case that somehow impacted the volume), and this produced the data in the Sample Measurements Table below:

Sample Measurements Table
Time Volume of Liquid in Bottles of Lubricant (in Ounces)
8:00am 30.03
9:00am 30.04
10:00am 29.98
11:00am 30.01
12:00pm 30.00
1:00pm 29.97
2:00pm 30.08
3:00pm 29.98
4:00pm 29.99
5:00pm 29.98
Mean (M) 30.006
• Analyze this operations management issue.
• Provide the algebraic equation for the UCL and for the LCL (using UCL, LCL, M, and SD as variables).
• Calculate and provide the numerical ULC and LCL values.

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