(SEF) Lecture 9 - Software Quality Assurance

Software Quality

What is defined by the term ‘‘software quality’?

• Good software should be reliable, efficient, maintanable, and meet user needs.

• It should deliver high performance w minimal defects.

Types of Software Quality

There are 2 types of software quality, write it down and explain.

1. Quality of Design

   • Ensure requirements, specifications, and design are correct.

2. Quality of Conformance

   • Ensures implementation follows the design and requirements correctly.

Factos Affecting Quality

What are the factors that affect a software’s quality?

1. Customers blame devs for bad software

2. Devs blame customers for unrealistic expectations, constant changes and deadlines.

Software Quality Dimensions

What are 8 of David Garvin’s software quality dimensions?

(P.P.A.S.D.C.R.F)

1. Performance Quality → does it meet user expectations?

2. Perception Quality → Do customers think it is high quality?

3. Aesthetics → user friendly and visually appealing?

4. Serviceability → can it be easily maintained and debugged?

5. Durability → can s/ware be modified w/out issues?

6. Conformance → s/ware follow standards?

7. Reliability → Does it run w/out failure?

8. Feature Quality → have useful features?

McCall’s Software Quality Factors

explain 3 categories of mccall’’s sware quality factors.

1. Product Operations (Functionality)

   • Correctness

   • Reliability

   • Efficiency

   • Integrity

   • Usability

2. Product Revision (Maintainability)

   • Maintainability

   • Flexibility

   • Testability

3. Product Transition (Adaptability)

   • Portability

   • Reusability

   • Interoperability (can it connect w other systems?)

Software Quality Assurance

What is SQA?

• A process to ensure that the developed software meets high standards.

• Helps in error detection, error prevention, and control.

Key Activities in SQA

What are all the key activities in SQA?

1. Standards Compliance – Follows industry standards.

2. Reviews & Audits – Checks software at each stage.

3. Testing – Detects defects before release.

4. Defect Analysis – Identifies root causes of errors.

5. Change Management – Tracks and controls modifications.

6. Security & Risk Management – Ensures safe and stable software.

SQA Group Responsibilities

What are the group responsibilities in the SQA process?

• Prepares an SQA plan outlining evaluations, reviews, and audits.

• Ensures compliance with internal and external standards (e.g., ISO-9001).

• Tracks issues and ensures they are fixed before release.

Achieving Software Quality

How do you achieve software quality?

• Good Project Management – Planning quality measures early.

• Effective Quality Control – Inspections, reviews, and testing.

• Quality Assurance – Auditing the project to ensure compliance.

Statistical SQA Process

Some processes of SQA include…?

1. Collect & categorize defects.

2. Identify root causes.

3. Use the Pareto Principle (80/20 Rule) – Fix the 20% of issues causing 80% of problems.

4. Implement fixes to prevent defects.

Common Causes of Software Defects

Explain. and list.

• Incomplete or incorrect specifications.

• Miscommunication with customers.

• Deviation from coding standards.

• Errors in design or programming logic.

Software Reliability & Safety

Explain the definition and formula..?

• Definition: The probability of failure-free operation for a specified time.

• Formula:
  Reliability(MTBeforeF)=Mean Time To Failure (MTTF)+Mean Time To Repair (MTTR)

• Availability:
  → Availability = [ MTTF / (MTTF + MTTR) ] x 100%

Higher MTTF → More reliable software.

Software Safety

What are the components of ensuring software safety?

• Focuses on identifying and preventing hazards that can cause failure.

• Critical in life-threatening systems (e.g., medical software, aviation).

Types of S/ware Quality Standards

There are 3 popular examples, explain them.

• ISO 9001: Defines quality management system for organizations.

• Capability Maturity Model (CMM): Evaluates software development maturity (Levels 1-5).

  • Initial – No defined process.

  • Managed – Basic project tracking.

  • Defined – Standardized processes.

  • Quantitatively Managed – Measured and controlled.

  • Optimizing – Continuous improvement.

• Six Sigma: Aims for 3.4 defects per million operations (very high quality).

Cost of Quality

List down and briefly explain the categories of quality costs.

1. Prevention Costs – Costs related to planning and training.

2. Internal Failure Costs – Costs from fixing defects before release.

3. External Failure Costs – Costly fixes after release (e.g., refunds, lawsuits).

• Finding and fixing defects early is cheaper than fixing them after release.

“Good Enough” Software

Explain.

• Some companies release software with minor known bugs.

• Risky for small companies → Bad reputation can cause business failure.

• Critical applications (e.g., healthcare) must not use this approach.