Defect prevention

Defect prevention is SQA technique the purpose of which is to identify root causes of defects and prevent them from reoccurring. Defect prevention is one of the important activity of the QA the purpose of which is to identify root cause of the reoccurring defects and prevent them from reoccurring again because reoccurring defects are very costly and wastage of time. This technique is helpful and can be used in all phases of SDLC to filter defects in each phase such that at the we have a product with minimum number of defects, since we can't expect software to 100% defect free so the term minimum number of defects is used in this context.

 Defect Detection and Reduction 

                         

it's another very important QA technique, as we by applying the defect prevention we still can have defect in the software product so to reduce the defect to as minimum level as possible we need effective techniques to remove the injected defect as possible under the project constraints, Defect detection is to detect defect that is injected in the software product and to reduce them.


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Impact of Missing software quality requirements

Missing quality requirements in software can impact both customer and supplier for example customer may face with physical injury or even death or loss of other financial data on the other hand supplier can also loss reputation loss of trust from the clients, financial loss, loss of employees. To analyze the impact various methods are used one method is of cost analysis based approach.

Cost analysis based approach

This approach is based on the assumption that measuring the cost of missing quality to calculate its impact and the resulting damage of missing that quality requirement. According to Eppler and Helfert principles cost are classified into two categories: Direct Cost and Indirect Cost.

Direct Cost

Direct cost is the cost that is visible, tangible and directly observable for example physical injury, financial loss, loss of people.

Indirect Cost

Indirect cost is the cost that is not observable easily and can impact on the long run such cost is difficult to measure because it's remain hidden for a long time for example loss of market share, loss of potential customer, loss of reputation in the market.

Impact analysis based approach

As mentioned above missing quality attribute in a software solution can impact both the customer and suppliers, in the worst case scenario people may exposed to the extent of death so impact analysis approach is based on the fact that one must perform the following.
Root cause analysis>> Identify problems >> Fix it >> keep going so that the corrective action is taken at the right time because once a failure occurs it would be difficult to circumvent with it.

Risk analysis based approach

Risk analysis based approach is also essential in determining cost of missing quality because in some cases the the time and place of missing quality event's is not easily determinable, in such scenario a method that is suited best is risk analysis, risk analysis approach is based on the fact of determining the probability of the risk that may occur and its potential loss a simple equation is derived in this approach which is below.
Risk Exposure = Probability of Risk * Potential Loss
the probability of risk and its impact is strongly related with the level of criticality of the software solution under observation following are the level of risk.

Level of Risk

The IEEE Standard for Software Verification and Validation has published the most broadly known scale of criticality in the IT domain. The standardized IT system criticality levels are as follows:

Level A: Catastrophic

• Continuous usage (24 hours per day)
• Irreversible environmental damages
• Loss of human lives o Disastrous economic or social impact

Level B: Critical

• Continuous usage (version change interruptions)
• Environmental damages
• Serious threats to human lives
• Permanent injury or severe illness
• Important economic or social impact.

Level C: Marginal

• Continuous usage with fix interruption periods
• Property damages o Minor injury or illness
• Significant economic or social impact.

Level D: Negligible

• Time-to-time usage
• Low property damages
• No risks on human lives
• Negligible economic or social impact.

what is software quality?

it is a subjective question mean every one define quality according to their own perspective but in simple words software quality can be defined is the totality of the desire features of a product with how ease it is to use these features and with certain level of performance that the user expect from the product while interacting with the product under certain environment for a certain period of time. software quality can also be defined is a software product that have minimum numbers of defects and which satisfy user needs. Note: As practically we can't expect software with zero defects so i have used the word minimum defects in the above line.

what is Defect Containment

Defect Containment in software quality engineering can be defined is the process of reducing the damage of a defect so that there is no global affect of the defect observable to users, in simple words if we perform all SQA activities but still there is a chance that we shall face with certain defects, this the aim of the defect containment is to contained the defect while reducing its damage or to keep the defect locally so that there is no global damage observable.