Defect Root Cause Analysis

    Root Cause Analysis is the technique of uncovering the primary cause of a problem. The root cause analysis of defects can be done using various techniques but we will focus on the 5W1H method here.

    5W1H Method

    This method involves answering the 5W (What, Where, Who, When) and 1H (How) questions and repeating the process until the primary cause is identified. The example provided is a situation where customers are frustrated and are complaining about incorrect Equated Monthly Installment (EMI) calculation.

    5W1H Question Example
    What What happened? EMI calculation is wrong.
    Where Where did it happen? EMI calculator page.
    When When did it happen? Whenever calculation is carried out.
    Who Who was involved? Loan Officer.
    How How did it happen? Values for Loan Amount, Interest Rate and Loan Tenure were input and Calculate button was pressed.
    Why Why did it happen? There was a coding error in the EMI calculation.

    Next, we need to apply the same process to the answer to the Why question.

    5W1H Question Example
    What What happened? There was a coding error in the EMI calculation.
    Where Where did it happen? Code.
    When When did it happen? Coding phase.
    Who Who was involved? Developer.
    How How did it happen? The formula for EMI calculation was wrong coded.
    Why Why did it happen? The requirements specification document incorrectly specified the formula for EMI calculation.

    This process can go on and on until the root cause is found. Example:

    • QUESTION: Why did the requirements specification document incorrectly specify the formula for EMI calculation?
    • ANSWER: The Product Owner misunderstood the formula for EMI calculation that resulted in an error in the Requirements Specification.

    Use of Root Cause Analysis

    Okay, so you found the root cause of a defect. Now, what?

    You won’t get any value out of the process unless you do something to reduce the chance of similar defects occurring in the future. If the root cause is due to a person, you might want to train or change the person; if it is due to a technology, you might want to enhance or change the technology; and, if it is due to a process, you might want to revise or enhance the process.

    In the EMI calculation defect example above, you might want to train the Product Owner on the topic of EMI calculations so that he / she will not repeat the mistake again. In fact, if it is felt that he / she lacks a general understanding of finances in general, it might be a good idea to provide him / her a training on that wide topic itself.

    Defects, Root Causes and Effects

    The root causes of defects are the earliest reasons behind the occurrence of defects. Effects are the consequences of failures (which are due to defects).

    In the EMI calculation example above:

    • “EMI calculation is wrong.” is the defect.
    • “The Product Owner misunderstood the formula for EMI calculation that resulted in an error in the Requirements Specification.” is the root cause.
    • “Customers are frustrated and complaining about incorrect Equated Monthly Installment (EMI) calculation.” is the effect.

    Last Updated on September 12, 2020 by STF