Problem solving rule-set and deductive reasoning for fault diagnosis

Problem solving rule set

Identifying a fault and its rectification is one of the major types of problems that we have to face in our personal and work lives. This in general is called Fault diagnosis and rectificaton. Abnormal and undesirable conditions in any human made and natural systems including human body fall under this category. Even police detection work is primarily of this type.

We already discussed use of personal rules in our daily life. Here we will discuss more complex use of special rule-set and associated reasoning for fault diagnosis and rectification in real life which in most cases is complex in nature.

In any diagnostic case, symptoms based suitable tests are common problem solving tools. But how to decide which test is to be carried out when usual tests fail to pinpoint the problem? Here deductive reasoning steps in.

Furthermore, symptoms are expressed by the patient in healthcare cases. It is up to the doctor to elicit the more useful and critical information from the patient by targeted questioning that home in to the solution more quickly with minimum number of pathological tests.

We will highlight here the importance of forming experience based powerful and complex rule-sets and related abstract principle through a series of diagnostic cases. 

These ultimately help solving quite complex and baffling real life problems quickly and surely.

Case example 1: A patient with a severe and persistent stomach pain

A patient was admitted to the emergency with severe stomach pain. It turned out that he had gone through three other good hospitals already with no improvement of condition after treatment. The doctor-in-charge now examined all the stomach related pathological test reports. He found no indication of the cause of the pain to be located in stomach area.

This is the primary rule-set - when the ailment is stomach related, carry out all the pathological tests related to stomach ailment. The previous three hospitals had done that and accordingly treated the patient, though without any success.

Fortunately our doctor remembered an infrequently occurring associated rule - sometimes severe and persistent stomach pain is also caused by a heart attack. It is not a common happening but nevertheless it has been observed in significant number of cases to be termed as a rule.   

An immediate ECG showed a case of major heart attack. The patient ultimately survived.

Common rule-sets for identifying the cause creating the harmful symptoms in a diagnostic and cure type of problem situation need always to be used with experience based deductive reasoning - not just blindly without thinking.

The reasoning in this case was - Stomach tests failed to show the cause to be located in stomach - then what are the possible alternative locations? - The pain is severe and persistent - so the cause is likely to be located in a  major organ - now the reasoner is likely to remember the secondary less frequent rule.

Analyzing the initial stomach test reports using the common rule-set, recognizing the importance of severity and persistence of pain and finally identifying the infrequent rule of heart attack causing such stomach pain as a likely case formed a successful use of compound rule-set enriched with deductive reasoning.

Case example 2: Diagnosing a difficult cough

Years ago I stayed away from home for two years due to job demands. Finally after two years I returned home with a bad racking cough that I could not get rid of. It took away my sleep and energy. For months I consulted physicians and specialists, underwent many diagnostic tests and took a series of prescribed medicines. Even alternative medicine path I tried. But nothing could reduce the intensity of the evil cough.

Then I thought of Dr. Mukherjee (name changed) whom I used to consult before. When I entered his chamber he greeted me—we knew each other well. Patiently he listened through what I had to say. My speaking was frequently interrupted by my constant companion cough.

He thought for a moment, took out a printed booklet from his desk drawer and started asking me a series of questions. As far as I remember he asked me five questions. Answer to each of the questions had to be yes or no. At the end of the questionnaire he concluded without any hesitation, “You have bronchial asthma. I am prescribing you an inhaler. You will get well soon, but in future also you may need to use the inhaler if you get this cough again.”

That was that. Within two weeks I got cured (for the time being) of the devil of a cough that tormented me for the interminable many months past.

I thought even then, how powerful that questionnaire is! There was no need to go through any diagnostic test at all—a few questions and the issue was settled for good. Can’t there be such powerful set of questions for solving other difficult issues, not only in health domain?

As an inquirer into the subject of Innovation & Problem Solving, I remembered that experience, evaluated it with a new mindset and understood to some extent its power. Even I went recently to see Dr. Mukherjee and asked him about the questions he had used for me. He smiled. It was eight years ago. Then he took out a booklet and showed a list of nine questions. Even though my memory fails many times, I was sure that these were not the questions he asked eight years ago. After a moment's thought though I understood what happened. To confirm I asked, “You had changed the questions in your own way, isn’t it?” “Yes”, he nodded.

He had applied his own experience based deductive reasoning on the standard rule-set available at that time.

I am reproducing below the questions to be asked to a patient for diagnosing whether he has bronchial asthma. These are taken from a standard printed help to practicing physicians.

“Questions to be asked to the patient:

  1. Have you had an attack or recurrent episodes of wheezing (high pitched whistling sounds when breathing out)?
  2. Do you have troublesome cough which is particularly worse at night or on waking?
  3. Are you awakened by coughing or difficult breathing?
  4. Do you cough or wheeze after physical activity (like games or exercise)?
  5. Does the patient experience breathing problems during a particular season?
  6. Do you cough, wheeze or develop chest tightness after exposure to airborne allergens or irritants e.g. smoke, perfumes, animal fur?
  7. Does the patient’s cold frequently “go to the chest” or take more than 10 days to resolve?
  8. Does the patient use medication when symptoms occur? How often?
  9. Are symptoms relieved when medication is used?

If answer is yes to any of the questions, a diagnosis of asthma should be considered.”


The rule-set was available to all other previous doctors I visited. Finally Dr. Mukherjee only used it.

He had not only the advantage of referring to the previous test and treatment results, but also had suitably modified the standard questionnaire based on his experience. The previous tests together with the standard rule-set and my doctor's deductive reasoning formed a successful use of a compound rule-set.

Disclaimer: If you attract such a bad cough please consult a registered physician - just don't try to treat yourself by the rule-set elaborated above.

Personal rule-sets in daily life

You have perhaps experienced such set of questions when availing of telephonic support for some of your gadgets at home going faulty. Fault diagnosis is similar to disease diagnosis. Practitioners in any fault diagnostics domain can carefully form such a set of leading questions from long experience to screen out most of the common faults. The faults still not resolved after the questions should be tackled with more detailed attention. This powerful rule-set mechanism is used often for quick diagnosis and rectification.

Case example 3: Windows explorer not opening

Windows explorer in your laptop was not opening at all though you could execute other programs available. You remembered that your DVD drive misbehaved half an hour back and you had to pull out the half inserted DVD using a forceps (imagine!).

You just rebooted the laptop and everything worked fine.


This rule-set is based on a powerful principle,

Identify and treat the hardware related causes first and then only focus on the software related cause.

In essence, this problem solving principle says:

In any live system all software related symptoms and causes are masked by the hardware related causes. Thus in a complex and persistent presentation of adverse symptoms, Identify and treat the hardware related causes first and then only focus on the software related cause.

We will deal with this principle later in more detail.

In this case example, you had prior experience of the power of input-oputput device malfunctions over software related causes in a Windows PC. Additionally you knew the rule,

Many Windows PC or computer related problems can be resolved just by a reboot.

This in abstraction may be termed as refreshing, and in itself a powerful problem solving technique. Use of the hardware over software principle and the reboot rule in conjunction with your deductive reasoning resolved your problem.

To clarify definitions, a rule-set is a Problem Solving Tool and the method to use the rule-set for problem solving is the Problem Solving Technique.


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