Software Quality Metrics : Introduction

• Software quality metrics means the ability of a software product to be and to perform as per the standard defined. Metric means standards.
• The software quality metrics ensures that the software product is of highest quality and standard.
• There are three major software quality metrics. These are:

Software Quality Metrics

Software Quality Metrics : Customer Problem Metrics

• The quality metrics used in software industry that is responsible for measuring the problems encountered by the customers while using the product.
• From the customers point of view, all the problems they encountered while using the software product are problems with the software including the valid defects.
• The usability problems, unclear documentation and errors are the problems that cannot be considered as valid defects.
• The customer problem metrics is usually expressed in terms of problems per unit month i.e. PUM.

Software Quality Metrics : Customer Satisfaction Metrics

• Customer Satisfaction Metric deals with the overall quality of the product and how much a customer is satisfied with that software product.
• Customer satisfaction is often measured by customers survey data via a five point scale. These are:
  1. Very Satisfied.
  2. Satisfied.
  3. Neutral.
  4. Dissatisfied.
  5. Very Dissatisfied.

Customer Satisfaction Metrics

• Based on a five point scale data, several metrics with slight variations can be constructed and used. These are:
1. Percentages of completely satisfied customers.
2. Percentage of satisfied customers.
3. Percentage of dissatisfied customers.
4. Percentage of non-satisfied customers.

Note: Generally, ”Percentage of satisfied customers is used.”

• Net Satisfaction Index(NSI) is also used by some companies for customer satisfaction metrics.
• The net satisfaction index ha following weighing criteria:
  1. Completely Satisfied = 100%.
  2. Satisfied = 75%.
  3. Neutral = 50%.
  4. Dissatisfied = 25%.
  5. Completely Dissatisfied = 0%.

Software Quality Metrics : Software Maintenance Metrics

• A software product can be called as in maintenance phase when its development is complete and is released to the market.
• During this interval, the defect arrival by time interval and customer problem is called as de facto metrics.
• Also, the number of defect or problems arrived mainly depends upon the development phase and not on the maintenance phase.
• Therefore, certain metrics are required for software maintenance. These are:
1. Backlog Management Index(BMI)
• The metric that is used to manage the backlog of open and unresolved problems. It can be defined as:
  BMI = (Number of problems closed during the month * 100)/(Number of problems arrived during the month)
2. Fix Response Time(FRT)
• While developing the software product, certain guidelines regarding reporting of defect are made. It includes the guideline for time limit of fixes that must available against the reported defects.
• The fix response time for more severe defects is low and the fix response time for less severe defect is high.
• The fix response time metric can be calculated as:
  

  FRT = (Mean time of all problems from open to closed)

3. Fix Quality
• Fix quality of software product is the number of defects fixed.
• Every software product contains defects. But, Fix Quality ensures that the defects in software product are fixed on time as per the quality standard.
• Fix quality ensures that the fixes for the defects should not turn out to be defective.
• A fix can be called as defective if it does not fixes the problems and generates new problems in that software product.