Software Quality Metrics

Software Quality Tutorial



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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:

 

This images describes the types of Software Quality Metrics on which quality of a software product depends.

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.


PUM = Total problems reported by a customer for a period of time + Total number of license months of the software during the per

Here,

No of license months = Number of install licenses of software * Number of months in calculation period.

 

  • PUM is usually calculated for each month after the software is released to the market, and also for monthly averages by year.

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.

 

This image describes the Customer Satisfaction Metrics in software quality.

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)
  1. 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)

  1. 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.